"sleep with one eye open" meaning in English

{
  "etymology_text": "Some animals sleep with one eye open, so as to remain alert to threats.",
  "forms": [
    {
      "form": "sleeps with one eye open",
      "tags": [
        "present",
        "singular",
        "third-person"
      ]
    },
    {
      "form": "sleeping with one eye open",
      "tags": [
        "participle",
        "present"
      ]
    },
    {
      "form": "slept with one eye open",
      "tags": [
        "participle",
        "past"
      ]
    },
    {
      "form": "slept with one eye open",
      "tags": [
        "past"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {
        "1": "sleep<,,slept> with one eye open"
      },
      "expansion": "sleep with one eye open (third-person singular simple present sleeps with one eye open, present participle sleeping with one eye open, simple past and past participle slept with one eye open)",
      "name": "en-verb"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "verb",
  "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 entries with topic categories using raw markup",
          "parents": [
            "Entries with topic categories using raw markup",
            "Entry maintenance"
          ],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "English terms with non-redundant non-automated sortkeys",
          "parents": [
            "Terms with non-redundant non-automated sortkeys",
            "Entry maintenance"
          ],
          "source": "w"
        },
        {
          "kind": "topical",
          "langcode": "en",
          "name": "Sleep",
          "orig": "en:Sleep",
          "parents": [
            "Body",
            "Human",
            "All topics",
            "Fundamental"
          ],
          "source": "w"
        }
      ],
      "glosses": [
        "To remain vigilant at all times, especially by remaining partially awake or sleeping only lightly so as to avoid being caught off guard."
      ],
      "id": "en-sleep_with_one_eye_open-en-verb-wrIDq4hI",
      "links": [
        [
          "vigilant",
          "vigilant"
        ],
        [
          "off guard",
          "off guard"
        ]
      ],
      "raw_glosses": [
        "(figurative) To remain vigilant at all times, especially by remaining partially awake or sleeping only lightly so as to avoid being caught off guard."
      ],
      "tags": [
        "figuratively"
      ],
      "translations": [
        {
          "code": "fi",
          "lang": "Finnish",
          "sense": "Translations",
          "word": "nukkua toinen silmä auki"
        },
        {
          "code": "fr",
          "lang": "French",
          "sense": "Translations",
          "word": "ne dormir que d’un œil"
        },
        {
          "code": "pl",
          "lang": "Polish",
          "sense": "Translations",
          "tags": [
            "imperfective"
          ],
          "word": "spać z jednym okiem otwartym"
        },
        {
          "code": "pt",
          "lang": "Portuguese",
          "sense": "Translations",
          "word": "dormir com um olho aberto"
        }
      ]
    }
  ],
  "word": "sleep with one eye open"
}

{
  "etymology_text": "Some animals sleep with one eye open, so as to remain alert to threats.",
  "forms": [
    {
      "form": "sleeps with one eye open",
      "tags": [
        "present",
        "singular",
        "third-person"
      ]
    },
    {
      "form": "sleeping with one eye open",
      "tags": [
        "participle",
        "present"
      ]
    },
    {
      "form": "slept with one eye open",
      "tags": [
        "participle",
        "past"
      ]
    },
    {
      "form": "slept with one eye open",
      "tags": [
        "past"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {
        "1": "sleep<,,slept> with one eye open"
      },
      "expansion": "sleep with one eye open (third-person singular simple present sleeps with one eye open, present participle sleeping with one eye open, simple past and past participle slept with one eye open)",
      "name": "en-verb"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "verb",
  "senses": [
    {
      "categories": [
        "English entries with incorrect language header",
        "English entries with topic categories using raw markup",
        "English lemmas",
        "English multiword terms",
        "English terms with non-redundant non-automated sortkeys",
        "English verbs",
        "Translation table header lacks gloss",
        "en:Sleep"
      ],
      "glosses": [
        "To remain vigilant at all times, especially by remaining partially awake or sleeping only lightly so as to avoid being caught off guard."
      ],
      "links": [
        [
          "vigilant",
          "vigilant"
        ],
        [
          "off guard",
          "off guard"
        ]
      ],
      "raw_glosses": [
        "(figurative) To remain vigilant at all times, especially by remaining partially awake or sleeping only lightly so as to avoid being caught off guard."
      ],
      "tags": [
        "figuratively"
      ]
    }
  ],
  "translations": [
    {
      "code": "fi",
      "lang": "Finnish",
      "sense": "Translations",
      "word": "nukkua toinen silmä auki"
    },
    {
      "code": "fr",
      "lang": "French",
      "sense": "Translations",
      "word": "ne dormir que d’un œil"
    },
    {
      "code": "pl",
      "lang": "Polish",
      "sense": "Translations",
      "tags": [
        "imperfective"
      ],
      "word": "spać z jednym okiem otwartym"
    },
    {
      "code": "pt",
      "lang": "Portuguese",
      "sense": "Translations",
      "word": "dormir com um olho aberto"
    }
  ],
  "word": "sleep with one eye open"
}