"de tête" meaning in French

{
  "head_templates": [
    {
      "args": {},
      "expansion": "de tête",
      "name": "fr-prep phrase"
    }
  ],
  "lang": "French",
  "lang_code": "fr",
  "pos": "prep_phrase",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "French entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w"
        }
      ],
      "examples": [
        {
          "english": "to calculate a square root in one's head",
          "text": "calculer de tête une racine carrée",
          "type": "example"
        },
        {
          "english": "He recited hundreds of verses from the Odyssey.",
          "text": "Il a récité de tête des centaines de vers de l’Odyssée.",
          "type": "example"
        }
      ],
      "glosses": [
        "only with one's mind or memory, with no external aid, in one's head"
      ],
      "id": "en-de_tête-fr-prep_phrase-xVmRhHXX",
      "links": [
        [
          "in one's head",
          "in one's head"
        ]
      ],
      "related": [
        {
          "word": "de mémoire"
        },
        {
          "word": "comme ça"
        }
      ]
    }
  ],
  "sounds": [
    {
      "ipa": "/də tɛt/"
    },
    {
      "audio": "Fr-Paris--de tête.ogg",
      "mp3_url": "https://upload.wikimedia.org/wikipedia/commons/transcoded/d/d5/Fr-Paris--de_t%C3%AAte.ogg/Fr-Paris--de_t%C3%AAte.ogg.mp3",
      "ogg_url": "https://upload.wikimedia.org/wikipedia/commons/d/d5/Fr-Paris--de_t%C3%AAte.ogg",
      "tags": [
        "Paris"
      ],
      "text": "Audio (Paris)"
    }
  ],
  "word": "de tête"
}

{
  "head_templates": [
    {
      "args": {},
      "expansion": "de tête",
      "name": "fr-prep phrase"
    }
  ],
  "lang": "French",
  "lang_code": "fr",
  "pos": "prep_phrase",
  "related": [
    {
      "word": "de mémoire"
    },
    {
      "word": "comme ça"
    }
  ],
  "senses": [
    {
      "categories": [
        "French entries with incorrect language header",
        "French lemmas",
        "French multiword terms",
        "French prepositional phrases",
        "French terms with IPA pronunciation",
        "French terms with audio links",
        "French terms with usage examples"
      ],
      "examples": [
        {
          "english": "to calculate a square root in one's head",
          "text": "calculer de tête une racine carrée",
          "type": "example"
        },
        {
          "english": "He recited hundreds of verses from the Odyssey.",
          "text": "Il a récité de tête des centaines de vers de l’Odyssée.",
          "type": "example"
        }
      ],
      "glosses": [
        "only with one's mind or memory, with no external aid, in one's head"
      ],
      "links": [
        [
          "in one's head",
          "in one's head"
        ]
      ]
    }
  ],
  "sounds": [
    {
      "ipa": "/də tɛt/"
    },
    {
      "audio": "Fr-Paris--de tête.ogg",
      "mp3_url": "https://upload.wikimedia.org/wikipedia/commons/transcoded/d/d5/Fr-Paris--de_t%C3%AAte.ogg/Fr-Paris--de_t%C3%AAte.ogg.mp3",
      "ogg_url": "https://upload.wikimedia.org/wikipedia/commons/d/d5/Fr-Paris--de_t%C3%AAte.ogg",
      "tags": [
        "Paris"
      ],
      "text": "Audio (Paris)"
    }
  ],
  "word": "de tête"
}