"mean motion" meaning in English

{
  "forms": [
    {
      "form": "mean motions",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "mean motion (plural mean motions)",
      "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": "topical",
          "langcode": "en",
          "name": "Astronomy",
          "orig": "en:Astronomy",
          "parents": [
            "Sciences",
            "Space",
            "All topics",
            "Nature",
            "Fundamental"
          ],
          "source": "w"
        }
      ],
      "glosses": [
        "An angle of τ (radians) divided by the orbital period (of a celestial body in an elliptic orbit)."
      ],
      "id": "en-mean_motion-en-noun-f67QoCLT",
      "links": [
        [
          "astronomy",
          "astronomy"
        ],
        [
          "radian",
          "radian"
        ],
        [
          "orbital period",
          "orbital period"
        ]
      ],
      "qualifier": "celestial mechanics",
      "raw_glosses": [
        "(astronomy, celestial mechanics) An angle of τ (radians) divided by the orbital period (of a celestial body in an elliptic orbit)."
      ],
      "topics": [
        "astronomy",
        "natural-sciences"
      ],
      "wikipedia": [
        "mean motion"
      ]
    }
  ],
  "word": "mean motion"
}

{
  "forms": [
    {
      "form": "mean motions",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "mean motion (plural mean motions)",
      "name": "en-noun"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        "English countable nouns",
        "English entries with incorrect language header",
        "English lemmas",
        "English multiword terms",
        "English nouns",
        "en:Astronomy"
      ],
      "glosses": [
        "An angle of τ (radians) divided by the orbital period (of a celestial body in an elliptic orbit)."
      ],
      "links": [
        [
          "astronomy",
          "astronomy"
        ],
        [
          "radian",
          "radian"
        ],
        [
          "orbital period",
          "orbital period"
        ]
      ],
      "qualifier": "celestial mechanics",
      "raw_glosses": [
        "(astronomy, celestial mechanics) An angle of τ (radians) divided by the orbital period (of a celestial body in an elliptic orbit)."
      ],
      "topics": [
        "astronomy",
        "natural-sciences"
      ],
      "wikipedia": [
        "mean motion"
      ]
    }
  ],
  "word": "mean motion"
}