"m/o" meaning in English

{
  "forms": [
    {
      "form": "o",
      "tags": [
        "canonical"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {
        "1": "en",
        "2": "noun"
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      "expansion": "o",
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  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
    {
      "alt_of": [
        {
          "word": "month(s) old"
        }
      ],
      "categories": [],
      "examples": [
        {
          "text": "baby Jackie is 5 m/o",
          "type": "example"
        }
      ],
      "glosses": [
        "Abbreviation of month(s) old."
      ],
      "id": "en-m/o-en-noun-fRHcxLHK",
      "links": [
        [
          "month",
          "month#English"
        ],
        [
          "old",
          "old#English"
        ]
      ],
      "tags": [
        "abbreviation",
        "alt-of"
      ]
    },
    {
      "categories": [
        {
          "kind": "topical",
          "langcode": "en",
          "name": "Chemistry",
          "orig": "en:Chemistry",
          "parents": [
            "Sciences",
            "All topics",
            "Fundamental"
          ],
          "source": "w"
        },
        {
          "_dis": "10 90",
          "kind": "other",
          "name": "English entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w+disamb"
        }
      ],
      "glosses": [
        "molar percent (percentage calculated by relative molarity [number of atoms or molecules])"
      ],
      "id": "en-m/o-en-noun-iX4CSmox",
      "links": [
        [
          "chemistry",
          "chemistry"
        ],
        [
          "molar",
          "molar"
        ],
        [
          "percent",
          "percent"
        ]
      ],
      "raw_glosses": [
        "(chemistry) molar percent (percentage calculated by relative molarity [number of atoms or molecules])"
      ],
      "related": [
        {
          "_dis1": "0 100",
          "word": "yo"
        }
      ],
      "synonyms": [
        {
          "word": "a/o"
        }
      ],
      "topics": [
        "chemistry",
        "natural-sciences",
        "physical-sciences"
      ]
    }
  ],
  "word": "m/o"
}

{
  "categories": [
    "English entries with incorrect language header",
    "English lemmas",
    "English nouns"
  ],
  "forms": [
    {
      "form": "o",
      "tags": [
        "canonical"
      ]
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  ],
  "head_templates": [
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      "args": {
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      "expansion": "o",
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  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "related": [
    {
      "word": "yo"
    }
  ],
  "senses": [
    {
      "alt_of": [
        {
          "word": "month(s) old"
        }
      ],
      "categories": [
        "English abbreviations",
        "English terms with usage examples"
      ],
      "examples": [
        {
          "text": "baby Jackie is 5 m/o",
          "type": "example"
        }
      ],
      "glosses": [
        "Abbreviation of month(s) old."
      ],
      "links": [
        [
          "month",
          "month#English"
        ],
        [
          "old",
          "old#English"
        ]
      ],
      "tags": [
        "abbreviation",
        "alt-of"
      ]
    },
    {
      "categories": [
        "en:Chemistry"
      ],
      "glosses": [
        "molar percent (percentage calculated by relative molarity [number of atoms or molecules])"
      ],
      "links": [
        [
          "chemistry",
          "chemistry"
        ],
        [
          "molar",
          "molar"
        ],
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          "percent",
          "percent"
        ]
      ],
      "raw_glosses": [
        "(chemistry) molar percent (percentage calculated by relative molarity [number of atoms or molecules])"
      ],
      "synonyms": [
        {
          "word": "a/o"
        }
      ],
      "topics": [
        "chemistry",
        "natural-sciences",
        "physical-sciences"
      ]
    }
  ],
  "word": "m/o"
}

{
  "called_from": "form_descriptions/2278",
  "msg": "suspicious alt_of/form_of with '(': month(s) old",
  "path": [
    "m/o"
  ],
  "section": "English",
  "subsection": "noun",
  "title": "m/o",
  "trace": ""
}