"pierhead line" meaning in English

{
  "forms": [
    {
      "form": "pierhead lines",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "pierhead line (plural pierhead lines)",
      "name": "en-noun"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "American English",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "English entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w"
        }
      ],
      "glosses": [
        "A line in a navigable waterway established by the Army Corps of Engineers, beyond which a pier cannot project."
      ],
      "id": "en-pierhead_line-en-noun-jm4A0Z~Y",
      "raw_glosses": [
        "(US) A line in a navigable waterway established by the Army Corps of Engineers, beyond which a pier cannot project."
      ],
      "related": [
        {
          "word": "bulkhead line"
        }
      ],
      "tags": [
        "US"
      ]
    }
  ],
  "word": "pierhead line"
}

{
  "forms": [
    {
      "form": "pierhead lines",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "pierhead line (plural pierhead lines)",
      "name": "en-noun"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "related": [
    {
      "word": "bulkhead line"
    }
  ],
  "senses": [
    {
      "categories": [
        "American English",
        "English countable nouns",
        "English entries with incorrect language header",
        "English lemmas",
        "English multiword terms",
        "English nouns"
      ],
      "glosses": [
        "A line in a navigable waterway established by the Army Corps of Engineers, beyond which a pier cannot project."
      ],
      "raw_glosses": [
        "(US) A line in a navigable waterway established by the Army Corps of Engineers, beyond which a pier cannot project."
      ],
      "tags": [
        "US"
      ]
    }
  ],
  "word": "pierhead line"
}