"Class M" meaning in English

{
  "etymology_text": "Originally from the TV series Star Trek.",
  "head_templates": [
    {
      "args": {
        "1": "-",
        "head": "Class M"
      },
      "expansion": "Class M (not comparable)",
      "name": "en-adj"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "adj",
  "senses": [
    {
      "categories": [
        {
          "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"
        },
        {
          "kind": "topical",
          "langcode": "en",
          "name": "Science fiction",
          "orig": "en:Science fiction",
          "parents": [
            "Fiction",
            "Speculative fiction",
            "Artistic works",
            "Genres",
            "Art",
            "Entertainment",
            "Culture",
            "Society",
            "All topics",
            "Fundamental"
          ],
          "source": "w"
        },
        {
          "kind": "topical",
          "langcode": "en",
          "name": "Star Trek",
          "orig": "en:Star Trek",
          "parents": [
            "American fiction",
            "Film",
            "Science fiction",
            "Television",
            "Fiction",
            "United States",
            "Entertainment",
            "Mass media",
            "Speculative fiction",
            "Broadcasting",
            "Artistic works",
            "North America",
            "Culture",
            "Media",
            "Genres",
            "Telecommunications",
            "Art",
            "America",
            "Society",
            "Communication",
            "Technology",
            "Earth",
            "All topics",
            "Nature",
            "Fundamental"
          ],
          "source": "w"
        }
      ],
      "glosses": [
        "Of a planet: having characteristics similar to that of Earth."
      ],
      "id": "en-Class_M-en-adj-kKEDdLjm",
      "links": [
        [
          "science fiction",
          "science fiction"
        ],
        [
          "planet",
          "planet"
        ],
        [
          "characteristic",
          "characteristic"
        ],
        [
          "Earth",
          "Earth"
        ]
      ],
      "raw_glosses": [
        "(science fiction) Of a planet: having characteristics similar to that of Earth."
      ],
      "synonyms": [
        {
          "word": "class M"
        }
      ],
      "tags": [
        "not-comparable"
      ],
      "topics": [
        "literature",
        "media",
        "publishing",
        "science-fiction"
      ],
      "wikipedia": [
        "Class M planet",
        "Star Trek"
      ]
    }
  ],
  "word": "Class M"
}

{
  "etymology_text": "Originally from the TV series Star Trek.",
  "head_templates": [
    {
      "args": {
        "1": "-",
        "head": "Class M"
      },
      "expansion": "Class M (not comparable)",
      "name": "en-adj"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "adj",
  "senses": [
    {
      "categories": [
        "English adjectives",
        "English entries with incorrect language header",
        "English lemmas",
        "English multiword terms",
        "English terms derived from Star Trek",
        "English uncomparable adjectives",
        "Pages with 1 entry",
        "Pages with entries",
        "en:Science fiction",
        "en:Star Trek"
      ],
      "glosses": [
        "Of a planet: having characteristics similar to that of Earth."
      ],
      "links": [
        [
          "science fiction",
          "science fiction"
        ],
        [
          "planet",
          "planet"
        ],
        [
          "characteristic",
          "characteristic"
        ],
        [
          "Earth",
          "Earth"
        ]
      ],
      "raw_glosses": [
        "(science fiction) Of a planet: having characteristics similar to that of Earth."
      ],
      "tags": [
        "not-comparable"
      ],
      "topics": [
        "literature",
        "media",
        "publishing",
        "science-fiction"
      ],
      "wikipedia": [
        "Class M planet",
        "Star Trek"
      ]
    }
  ],
  "synonyms": [
    {
      "word": "class M"
    }
  ],
  "word": "Class M"
}