"salt line" meaning in English

{
  "forms": [
    {
      "form": "salt lines",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "salt line (plural salt lines)",
      "name": "en-noun"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "English entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "English entries with topic categories using raw markup",
          "parents": [
            "Entries with topic categories using raw markup",
            "Entry maintenance"
          ],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "English terms with non-redundant non-automated sortkeys",
          "parents": [
            "Terms with non-redundant non-automated sortkeys",
            "Entry maintenance"
          ],
          "source": "w"
        },
        {
          "kind": "topical",
          "langcode": "en",
          "name": "Geography",
          "orig": "en:Geography",
          "parents": [
            "Earth sciences",
            "Sciences",
            "All topics",
            "Fundamental"
          ],
          "source": "w"
        }
      ],
      "glosses": [
        "a boundary between brackish and fresh water between or within bodies of water."
      ],
      "id": "en-salt_line-en-noun-r5Xli3Fc",
      "links": [
        [
          "brackish",
          "brackish"
        ],
        [
          "water",
          "water"
        ]
      ],
      "related": [
        {
          "word": "salt front"
        },
        {
          "word": "salt wedge"
        }
      ]
    }
  ],
  "word": "salt line"
}

{
  "forms": [
    {
      "form": "salt lines",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "salt line (plural salt lines)",
      "name": "en-noun"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "related": [
    {
      "word": "salt front"
    },
    {
      "word": "salt wedge"
    }
  ],
  "senses": [
    {
      "categories": [
        "English countable nouns",
        "English entries with incorrect language header",
        "English entries with topic categories using raw markup",
        "English lemmas",
        "English multiword terms",
        "English nouns",
        "English terms with non-redundant non-automated sortkeys",
        "en:Geography"
      ],
      "glosses": [
        "a boundary between brackish and fresh water between or within bodies of water."
      ],
      "links": [
        [
          "brackish",
          "brackish"
        ],
        [
          "water",
          "water"
        ]
      ]
    }
  ],
  "word": "salt line"
}