"třenák" meaning in Czech

{
  "head_templates": [
    {
      "args": {
        "1": "m-in"
      },
      "expansion": "třenák m inan",
      "name": "cs-noun"
    }
  ],
  "lang": "Czech",
  "lang_code": "cs",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "Czech 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": "cs",
          "name": "Teeth",
          "orig": "cs:Teeth",
          "parents": [
            "Mouth",
            "Face",
            "Head and neck",
            "Body parts",
            "Body",
            "Anatomy",
            "All topics",
            "Biology",
            "Medicine",
            "Fundamental",
            "Sciences",
            "Healthcare",
            "Health"
          ],
          "source": "w"
        }
      ],
      "glosses": [
        "premolar"
      ],
      "id": "en-třenák-cs-noun-gelRI1PZ",
      "links": [
        [
          "premolar",
          "premolar"
        ]
      ],
      "raw_glosses": [
        "(informal) premolar"
      ],
      "synonyms": [
        {
          "word": "třenový zub"
        }
      ],
      "tags": [
        "inanimate",
        "informal",
        "masculine"
      ]
    }
  ],
  "sounds": [
    {
      "ipa": "[ˈtr̝̊ɛnaːk]"
    }
  ],
  "word": "třenák"
}

{
  "head_templates": [
    {
      "args": {
        "1": "m-in"
      },
      "expansion": "třenák m inan",
      "name": "cs-noun"
    }
  ],
  "lang": "Czech",
  "lang_code": "cs",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        "Czech entries with incorrect language header",
        "Czech inanimate nouns",
        "Czech informal terms",
        "Czech lemmas",
        "Czech masculine nouns",
        "Czech nouns",
        "Czech terms with IPA pronunciation",
        "Pages with 1 entry",
        "Pages with entries",
        "cs:Teeth"
      ],
      "glosses": [
        "premolar"
      ],
      "links": [
        [
          "premolar",
          "premolar"
        ]
      ],
      "raw_glosses": [
        "(informal) premolar"
      ],
      "synonyms": [
        {
          "word": "třenový zub"
        }
      ],
      "tags": [
        "inanimate",
        "informal",
        "masculine"
      ]
    }
  ],
  "sounds": [
    {
      "ipa": "[ˈtr̝̊ɛnaːk]"
    }
  ],
  "word": "třenák"
}