"ач" meaning in Mongolian

{
  "forms": [
    {
      "form": "ač",
      "tags": [
        "romanization"
      ]
    },
    {
      "form": "ᠠᠴᠢ",
      "roman": "ači",
      "tags": [
        "Mongolian"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {
        "1": "ᠠᠴᠢ"
      },
      "expansion": "ач • (ač) (Mongolian spelling ᠠᠴᠢ (ači))",
      "name": "mn-noun"
    }
  ],
  "lang": "Mongolian",
  "lang_code": "mn",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "Mongolian entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Mongolian entries with topic categories using raw markup",
          "parents": [
            "Entries with topic categories using raw markup",
            "Entry maintenance"
          ],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Mongolian terms with redundant script codes",
          "parents": [
            "Terms with redundant script codes",
            "Entry maintenance"
          ],
          "source": "w"
        },
        {
          "kind": "topical",
          "langcode": "mn",
          "name": "Family",
          "orig": "mn:Family",
          "parents": [
            "People",
            "Human",
            "All topics",
            "Fundamental"
          ],
          "source": "w"
        }
      ],
      "glosses": [
        "grandson"
      ],
      "id": "en-ач-mn-noun-hkTIr4nx",
      "links": [
        [
          "grandson",
          "grandson"
        ]
      ]
    }
  ],
  "word": "ач"
}

{
  "forms": [
    {
      "form": "ač",
      "tags": [
        "romanization"
      ]
    },
    {
      "form": "ᠠᠴᠢ",
      "roman": "ači",
      "tags": [
        "Mongolian"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {
        "1": "ᠠᠴᠢ"
      },
      "expansion": "ач • (ač) (Mongolian spelling ᠠᠴᠢ (ači))",
      "name": "mn-noun"
    }
  ],
  "lang": "Mongolian",
  "lang_code": "mn",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        "Mongolian 1-syllable words",
        "Mongolian entries with incorrect language header",
        "Mongolian entries with topic categories using raw markup",
        "Mongolian lemmas",
        "Mongolian nouns",
        "Mongolian terms with redundant script codes",
        "Requests for pronunciation in Mongolian entries",
        "mn:Family"
      ],
      "glosses": [
        "grandson"
      ],
      "links": [
        [
          "grandson",
          "grandson"
        ]
      ]
    }
  ],
  "word": "ач"
}