"listen up" meaning in English

{
  "etymology_templates": [
    {
      "args": {
        "1": "en",
        "2": "listen",
        "3": "up"
      },
      "expansion": "listen + up",
      "name": "com"
    }
  ],
  "etymology_text": "From listen + up. First use appears c. 1933, although the exact date of its first use is uncertain. See cite below.",
  "forms": [
    {
      "form": "listens up",
      "tags": [
        "present",
        "singular",
        "third-person"
      ]
    },
    {
      "form": "listening up",
      "tags": [
        "participle",
        "present"
      ]
    },
    {
      "form": "listened up",
      "tags": [
        "participle",
        "past"
      ]
    },
    {
      "form": "listened up",
      "tags": [
        "past"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {
        "1": "*"
      },
      "expansion": "listen up (third-person singular simple present listens up, present participle listening up, simple past and past participle listened up)",
      "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 phrasal verbs formed with \"up\"",
          "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 Danish translations",
          "parents": [],
          "source": "w"
        }
      ],
      "examples": [
        {
          "text": "I'm only gonna say this once, so you really need to listen up.",
          "type": "example"
        },
        {
          "ref": "1933, Eddie Dooley, Under the Goal Posts:",
          "text": "His sharp eyes scanned the faces of his charges. \"Listen up!\" he barked.",
          "type": "quote"
        }
      ],
      "glosses": [
        "To listen closely; to pay attention."
      ],
      "id": "en-listen_up-en-verb-CuwAVs~s",
      "links": [
        [
          "listen",
          "listen"
        ],
        [
          "pay attention",
          "pay attention"
        ]
      ],
      "raw_glosses": [
        "(idiomatic, informal) To listen closely; to pay attention."
      ],
      "tags": [
        "idiomatic",
        "informal"
      ],
      "translations": [
        {
          "code": "da",
          "lang": "Danish",
          "sense": "Translations",
          "word": "høre efter"
        }
      ]
    }
  ],
  "sounds": [
    {
      "audio": "En-au-listen up.ogg",
      "mp3_url": "https://upload.wikimedia.org/wikipedia/commons/transcoded/6/68/En-au-listen_up.ogg/En-au-listen_up.ogg.mp3",
      "ogg_url": "https://upload.wikimedia.org/wikipedia/commons/6/68/En-au-listen_up.ogg"
    }
  ],
  "word": "listen up"
}

{
  "etymology_templates": [
    {
      "args": {
        "1": "en",
        "2": "listen",
        "3": "up"
      },
      "expansion": "listen + up",
      "name": "com"
    }
  ],
  "etymology_text": "From listen + up. First use appears c. 1933, although the exact date of its first use is uncertain. See cite below.",
  "forms": [
    {
      "form": "listens up",
      "tags": [
        "present",
        "singular",
        "third-person"
      ]
    },
    {
      "form": "listening up",
      "tags": [
        "participle",
        "present"
      ]
    },
    {
      "form": "listened up",
      "tags": [
        "participle",
        "past"
      ]
    },
    {
      "form": "listened up",
      "tags": [
        "past"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {
        "1": "*"
      },
      "expansion": "listen up (third-person singular simple present listens up, present participle listening up, simple past and past participle listened up)",
      "name": "en-verb"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "verb",
  "senses": [
    {
      "categories": [
        "English compound terms",
        "English entries with incorrect language header",
        "English idioms",
        "English informal terms",
        "English lemmas",
        "English multiword terms",
        "English phrasal verbs",
        "English phrasal verbs formed with \"up\"",
        "English terms with quotations",
        "English terms with usage examples",
        "English verbs",
        "Entries with translation boxes",
        "Pages with 1 entry",
        "Pages with entries",
        "Terms with Danish translations",
        "Translation table header lacks gloss"
      ],
      "examples": [
        {
          "text": "I'm only gonna say this once, so you really need to listen up.",
          "type": "example"
        },
        {
          "ref": "1933, Eddie Dooley, Under the Goal Posts:",
          "text": "His sharp eyes scanned the faces of his charges. \"Listen up!\" he barked.",
          "type": "quote"
        }
      ],
      "glosses": [
        "To listen closely; to pay attention."
      ],
      "links": [
        [
          "listen",
          "listen"
        ],
        [
          "pay attention",
          "pay attention"
        ]
      ],
      "raw_glosses": [
        "(idiomatic, informal) To listen closely; to pay attention."
      ],
      "tags": [
        "idiomatic",
        "informal"
      ]
    }
  ],
  "sounds": [
    {
      "audio": "En-au-listen up.ogg",
      "mp3_url": "https://upload.wikimedia.org/wikipedia/commons/transcoded/6/68/En-au-listen_up.ogg/En-au-listen_up.ogg.mp3",
      "ogg_url": "https://upload.wikimedia.org/wikipedia/commons/6/68/En-au-listen_up.ogg"
    }
  ],
  "translations": [
    {
      "code": "da",
      "lang": "Danish",
      "sense": "Translations",
      "word": "høre efter"
    }
  ],
  "word": "listen up"
}