"trig pillar" meaning in English

{
  "forms": [
    {
      "form": "trig pillars",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "trig pillar (plural trig pillars)",
      "name": "en-noun"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "British English",
          "parents": [],
          "source": "w"
        },
        {
          "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": [
        {
          "ref": "2019, Alan Staniforth, Cleveland Way, page 64:",
          "text": "There are several prominent boundary stones close to the path which soon merges into a broad track as it heads towards the trig pillar on Round Hill.",
          "type": "quote"
        }
      ],
      "glosses": [
        "A triangulation pillar."
      ],
      "id": "en-trig_pillar-en-noun-MRdik7XG",
      "links": [
        [
          "triangulation pillar",
          "triangulation pillar"
        ]
      ],
      "raw_glosses": [
        "(UK) A triangulation pillar."
      ],
      "tags": [
        "UK"
      ]
    }
  ],
  "word": "trig pillar"
}

{
  "forms": [
    {
      "form": "trig pillars",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "trig pillar (plural trig pillars)",
      "name": "en-noun"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        "British English",
        "English countable nouns",
        "English entries with incorrect language header",
        "English lemmas",
        "English multiword terms",
        "English nouns",
        "English terms with quotations",
        "Pages with 1 entry",
        "Pages with entries"
      ],
      "examples": [
        {
          "ref": "2019, Alan Staniforth, Cleveland Way, page 64:",
          "text": "There are several prominent boundary stones close to the path which soon merges into a broad track as it heads towards the trig pillar on Round Hill.",
          "type": "quote"
        }
      ],
      "glosses": [
        "A triangulation pillar."
      ],
      "links": [
        [
          "triangulation pillar",
          "triangulation pillar"
        ]
      ],
      "raw_glosses": [
        "(UK) A triangulation pillar."
      ],
      "tags": [
        "UK"
      ]
    }
  ],
  "word": "trig pillar"
}