"one under" meaning in English

{
  "forms": [
    {
      "form": "one unders",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "one under (plural one unders)",
      "name": "en-noun"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "British English",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "English entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with 1 entry",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with entries",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "topical",
          "langcode": "en",
          "name": "Rail transportation",
          "orig": "en:Rail transportation",
          "parents": [
            "Transport",
            "All topics",
            "Fundamental"
          ],
          "source": "w"
        },
        {
          "kind": "topical",
          "langcode": "en",
          "name": "Suicide",
          "orig": "en:Suicide",
          "parents": [
            "Death",
            "Body",
            "Life",
            "All topics",
            "Nature",
            "Fundamental"
          ],
          "source": "w"
        }
      ],
      "examples": [
        {
          "text": "2002, \"Tube Troll\", \">Incident @ Hangar lane tube <\", uk.transport.london http://groups.google.com/group/uk.transport.london/browse_thread/thread/9a749f81e7f414b9/04825cc24c006db5?lnk=st&q=%22one+under%22+train&rnum=3#\nThe twist in this tale is that the driver (who was at the back and hadn't seen anything) booked off with stress (as drivers often do after a one under) and the guard who had been driving and witnessed the whold [sic] traumatic event had to creep into work the next day and pretend that nothing had happned..."
        },
        {
          "ref": "2004, \"Joe\", \"TV Alert: BBC3 9pm Trauma TONIGHT\", uk.railway http://groups.google.com/group/uk.railway/browse_thread/thread/dacc3df5d74e3501/4b2dff0298b19cc4?lnk=st&q=%22one+under%22+train&rnum=39#4b2dff0298b19cc4",
          "text": "About a one under on the Northern line."
        },
        {
          "text": "2005, \"Neilw001\", \"'One under'\", uk.transport.london http://groups.google.com/group/uk.transport.london/browse_thread/thread/2a2f71c4882d54ca/96db8446353aa28d?lnk=st&q=%22one+under%22+train&rnum=7#96db8446353aa28d\nI've been on a train when some [sic] has gone under. Actually heard the thump and then the driver on the radio saying \"I've got one under\"."
        }
      ],
      "glosses": [
        "A person under a train; a person hit by a train after jumping or falling in front of it."
      ],
      "id": "en-one_under-en-noun-DjEXzfP3",
      "links": [
        [
          "rail transport",
          "rail transport"
        ]
      ],
      "raw_glosses": [
        "(rail transport, slang, British) A person under a train; a person hit by a train after jumping or falling in front of it."
      ],
      "synonyms": [
        {
          "english": "London Underground, official",
          "word": "person under train"
        },
        {
          "tags": [
            "New-York"
          ],
          "word": "track pizza"
        }
      ],
      "tags": [
        "British",
        "slang"
      ],
      "topics": [
        "rail-transport",
        "railways",
        "transport"
      ]
    }
  ],
  "sounds": [
    {
      "audio": "En-au-one under.ogg",
      "mp3_url": "https://upload.wikimedia.org/wikipedia/commons/transcoded/c/c3/En-au-one_under.ogg/En-au-one_under.ogg.mp3",
      "ogg_url": "https://upload.wikimedia.org/wikipedia/commons/c/c3/En-au-one_under.ogg"
    }
  ],
  "word": "one under"
}

{
  "forms": [
    {
      "form": "one unders",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "one under (plural one unders)",
      "name": "en-noun"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        "British English",
        "English countable nouns",
        "English entries with incorrect language header",
        "English lemmas",
        "English multiword terms",
        "English nouns",
        "English slang",
        "Pages with 1 entry",
        "Pages with entries",
        "en:Rail transportation",
        "en:Suicide"
      ],
      "examples": [
        {
          "text": "2002, \"Tube Troll\", \">Incident @ Hangar lane tube <\", uk.transport.london http://groups.google.com/group/uk.transport.london/browse_thread/thread/9a749f81e7f414b9/04825cc24c006db5?lnk=st&q=%22one+under%22+train&rnum=3#\nThe twist in this tale is that the driver (who was at the back and hadn't seen anything) booked off with stress (as drivers often do after a one under) and the guard who had been driving and witnessed the whold [sic] traumatic event had to creep into work the next day and pretend that nothing had happned..."
        },
        {
          "ref": "2004, \"Joe\", \"TV Alert: BBC3 9pm Trauma TONIGHT\", uk.railway http://groups.google.com/group/uk.railway/browse_thread/thread/dacc3df5d74e3501/4b2dff0298b19cc4?lnk=st&q=%22one+under%22+train&rnum=39#4b2dff0298b19cc4",
          "text": "About a one under on the Northern line."
        },
        {
          "text": "2005, \"Neilw001\", \"'One under'\", uk.transport.london http://groups.google.com/group/uk.transport.london/browse_thread/thread/2a2f71c4882d54ca/96db8446353aa28d?lnk=st&q=%22one+under%22+train&rnum=7#96db8446353aa28d\nI've been on a train when some [sic] has gone under. Actually heard the thump and then the driver on the radio saying \"I've got one under\"."
        }
      ],
      "glosses": [
        "A person under a train; a person hit by a train after jumping or falling in front of it."
      ],
      "links": [
        [
          "rail transport",
          "rail transport"
        ]
      ],
      "raw_glosses": [
        "(rail transport, slang, British) A person under a train; a person hit by a train after jumping or falling in front of it."
      ],
      "tags": [
        "British",
        "slang"
      ],
      "topics": [
        "rail-transport",
        "railways",
        "transport"
      ]
    }
  ],
  "sounds": [
    {
      "audio": "En-au-one under.ogg",
      "mp3_url": "https://upload.wikimedia.org/wikipedia/commons/transcoded/c/c3/En-au-one_under.ogg/En-au-one_under.ogg.mp3",
      "ogg_url": "https://upload.wikimedia.org/wikipedia/commons/c/c3/En-au-one_under.ogg"
    }
  ],
  "synonyms": [
    {
      "english": "London Underground, official",
      "word": "person under train"
    },
    {
      "tags": [
        "New-York"
      ],
      "word": "track pizza"
    }
  ],
  "word": "one under"
}