"nothing if not" meaning in English

{
  "etymology_text": "Literally, asserts the truth of a statement by saying that the alternative is void.",
  "head_templates": [
    {
      "args": {
        "1": "-",
        "head": "nothing if not"
      },
      "expansion": "nothing if not (not comparable)",
      "name": "en-adv"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "adv",
  "senses": [
    {
      "antonyms": [
        {
          "word": "anything but"
        }
      ],
      "categories": [
        {
          "kind": "other",
          "name": "English 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"
        }
      ],
      "examples": [
        {
          "text": "Coordinate term: a bit"
        },
        {
          "text": "Near-synonyms: nothing less than, nothing but"
        },
        {
          "text": "He's nothing if not a liar.\nHe is certainly a liar.",
          "type": "example"
        },
        {
          "text": "Well, thrift is a virtue, and he's nothing if not careful with money.\nNot only denotes that he is certainly careful with money (frugal) but also obliquely implies that he is very careful with money (miserly).",
          "type": "example"
        }
      ],
      "glosses": [
        "Certainly; definitely; (sometimes also obliquely) thoroughly; wholly; to a high degree; extremely."
      ],
      "id": "en-nothing_if_not-en-adv-en:certainly__definitely__plus_or_minus_very",
      "links": [
        [
          "Certainly",
          "certainly"
        ],
        [
          "definitely",
          "definitely"
        ],
        [
          "oblique",
          "oblique"
        ],
        [
          "thoroughly",
          "thoroughly"
        ],
        [
          "wholly",
          "wholly"
        ],
        [
          "extremely",
          "extremely"
        ]
      ],
      "raw_glosses": [
        "(idiomatic) Certainly; definitely; (sometimes also obliquely) thoroughly; wholly; to a high degree; extremely."
      ],
      "senseid": [
        "en:certainly, definitely, plus-or-minus very"
      ],
      "tags": [
        "idiomatic",
        "not-comparable"
      ]
    }
  ],
  "sounds": [
    {
      "ipa": "/ˈnʌθɪŋ ɪf nɒt/",
      "tags": [
        "Received-Pronunciation"
      ]
    }
  ],
  "word": "nothing if not"
}

{
  "etymology_text": "Literally, asserts the truth of a statement by saying that the alternative is void.",
  "head_templates": [
    {
      "args": {
        "1": "-",
        "head": "nothing if not"
      },
      "expansion": "nothing if not (not comparable)",
      "name": "en-adv"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "adv",
  "senses": [
    {
      "antonyms": [
        {
          "word": "anything but"
        }
      ],
      "categories": [
        "English adverbs",
        "English entries with incorrect language header",
        "English idioms",
        "English lemmas",
        "English multiword terms",
        "English terms with usage examples",
        "English uncomparable adverbs",
        "Pages with 1 entry",
        "Pages with entries"
      ],
      "examples": [
        {
          "text": "Coordinate term: a bit"
        },
        {
          "text": "Near-synonyms: nothing less than, nothing but"
        },
        {
          "text": "He's nothing if not a liar.\nHe is certainly a liar.",
          "type": "example"
        },
        {
          "text": "Well, thrift is a virtue, and he's nothing if not careful with money.\nNot only denotes that he is certainly careful with money (frugal) but also obliquely implies that he is very careful with money (miserly).",
          "type": "example"
        }
      ],
      "glosses": [
        "Certainly; definitely; (sometimes also obliquely) thoroughly; wholly; to a high degree; extremely."
      ],
      "links": [
        [
          "Certainly",
          "certainly"
        ],
        [
          "definitely",
          "definitely"
        ],
        [
          "oblique",
          "oblique"
        ],
        [
          "thoroughly",
          "thoroughly"
        ],
        [
          "wholly",
          "wholly"
        ],
        [
          "extremely",
          "extremely"
        ]
      ],
      "raw_glosses": [
        "(idiomatic) Certainly; definitely; (sometimes also obliquely) thoroughly; wholly; to a high degree; extremely."
      ],
      "senseid": [
        "en:certainly, definitely, plus-or-minus very"
      ],
      "tags": [
        "idiomatic",
        "not-comparable"
      ]
    }
  ],
  "sounds": [
    {
      "ipa": "/ˈnʌθɪŋ ɪf nɒt/",
      "tags": [
        "Received-Pronunciation"
      ]
    }
  ],
  "word": "nothing if not"
}