"subluminal" meaning in English

{
  "etymology_templates": [
    {
      "args": {
        "1": "en",
        "2": "sub",
        "3": "luminal"
      },
      "expansion": "sub- + luminal",
      "name": "prefix"
    }
  ],
  "etymology_text": "From sub- + luminal.",
  "forms": [
    {
      "form": "more subluminal",
      "tags": [
        "comparative"
      ]
    },
    {
      "form": "most subluminal",
      "tags": [
        "superlative"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "subluminal (comparative more subluminal, superlative most subluminal)",
      "name": "en-adj"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "adj",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "English entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "English terms prefixed with sub-",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Entries with translation boxes",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with 1 entry",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with entries",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Terms with Greek translations",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Terms with Italian translations",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "topical",
          "langcode": "en",
          "name": "Relativity",
          "orig": "en:Relativity",
          "parents": [
            "Physics",
            "Sciences",
            "All topics",
            "Fundamental"
          ],
          "source": "w"
        }
      ],
      "glosses": [
        "slower than light; having a speed less than light."
      ],
      "id": "en-subluminal-en-adj-TUnGwgkL",
      "links": [
        [
          "speed",
          "speed"
        ],
        [
          "light",
          "light"
        ]
      ],
      "related": [
        {
          "word": "superluminal"
        },
        {
          "word": "transluminal"
        },
        {
          "word": "luminal"
        },
        {
          "word": "FTL"
        },
        {
          "word": "subsonic"
        }
      ],
      "synonyms": [
        {
          "word": "sublumic"
        },
        {
          "sense": "periphrastic",
          "topics": [
            "physics",
            "physical-sciences",
            "natural-sciences"
          ],
          "word": "causally reachable"
        }
      ],
      "translations": [
        {
          "code": "el",
          "lang": "Greek",
          "roman": "ypofototachikós",
          "sense": "Translations",
          "tags": [
            "masculine"
          ],
          "word": "υποφωτοταχικός"
        },
        {
          "code": "el",
          "lang": "Greek",
          "roman": "ypofototachikí",
          "sense": "Translations",
          "tags": [
            "feminine"
          ],
          "word": "υποφωτοταχική"
        },
        {
          "code": "el",
          "lang": "Greek",
          "roman": "ypofototachikó",
          "sense": "Translations",
          "tags": [
            "neuter"
          ],
          "word": "υποφωτοταχικό"
        },
        {
          "code": "it",
          "lang": "Italian",
          "sense": "Translations",
          "tags": [
            "feminine",
            "masculine"
          ],
          "word": "subluminale"
        }
      ]
    }
  ],
  "word": "subluminal"
}

{
  "etymology_templates": [
    {
      "args": {
        "1": "en",
        "2": "sub",
        "3": "luminal"
      },
      "expansion": "sub- + luminal",
      "name": "prefix"
    }
  ],
  "etymology_text": "From sub- + luminal.",
  "forms": [
    {
      "form": "more subluminal",
      "tags": [
        "comparative"
      ]
    },
    {
      "form": "most subluminal",
      "tags": [
        "superlative"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "subluminal (comparative more subluminal, superlative most subluminal)",
      "name": "en-adj"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "adj",
  "related": [
    {
      "word": "superluminal"
    },
    {
      "word": "transluminal"
    },
    {
      "word": "luminal"
    },
    {
      "word": "FTL"
    },
    {
      "word": "subsonic"
    }
  ],
  "senses": [
    {
      "categories": [
        "English adjectives",
        "English entries with incorrect language header",
        "English lemmas",
        "English terms prefixed with sub-",
        "Entries with translation boxes",
        "Pages with 1 entry",
        "Pages with entries",
        "Terms with Greek translations",
        "Terms with Italian translations",
        "Translation table header lacks gloss",
        "en:Relativity"
      ],
      "glosses": [
        "slower than light; having a speed less than light."
      ],
      "links": [
        [
          "speed",
          "speed"
        ],
        [
          "light",
          "light"
        ]
      ]
    }
  ],
  "synonyms": [
    {
      "word": "sublumic"
    },
    {
      "sense": "periphrastic",
      "topics": [
        "physics",
        "physical-sciences",
        "natural-sciences"
      ],
      "word": "causally reachable"
    }
  ],
  "translations": [
    {
      "code": "el",
      "lang": "Greek",
      "roman": "ypofototachikós",
      "sense": "Translations",
      "tags": [
        "masculine"
      ],
      "word": "υποφωτοταχικός"
    },
    {
      "code": "el",
      "lang": "Greek",
      "roman": "ypofototachikí",
      "sense": "Translations",
      "tags": [
        "feminine"
      ],
      "word": "υποφωτοταχική"
    },
    {
      "code": "el",
      "lang": "Greek",
      "roman": "ypofototachikó",
      "sense": "Translations",
      "tags": [
        "neuter"
      ],
      "word": "υποφωτοταχικό"
    },
    {
      "code": "it",
      "lang": "Italian",
      "sense": "Translations",
      "tags": [
        "feminine",
        "masculine"
      ],
      "word": "subluminale"
    }
  ],
  "word": "subluminal"
}