"one small step for man, one giant leap for mankind" meaning in English

{
  "etymology_text": "Spoken by Neil Armstrong when he first stepped onto the surface of the Moon. Armstrong intended to say \"one small step for a man\", but misspoke.http://www.snopes.com/quotes/onesmall.asp",
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      "expansion": "one small step for man, one giant leap for mankind",
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    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "phrase",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "English allusions",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "English entries with incorrect language header",
          "parents": [
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        {
          "kind": "topical",
          "langcode": "en",
          "name": "Astronautics",
          "orig": "en:Astronautics",
          "parents": [
            "Applied sciences",
            "Space",
            "Sciences",
            "Nature",
            "All topics",
            "Fundamental"
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        },
        {
          "kind": "topical",
          "langcode": "en",
          "name": "Historical events",
          "orig": "en:Historical events",
          "parents": [
            "History",
            "All topics",
            "Fundamental"
          ],
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        },
        {
          "kind": "topical",
          "langcode": "en",
          "name": "Moon",
          "orig": "en:Moon",
          "parents": [
            "Celestial bodies",
            "Light",
            "Moons",
            "Nature",
            "Space",
            "Energy",
            "All topics",
            "Fundamental"
          ],
          "source": "w"
        },
        {
          "kind": "topical",
          "langcode": "en",
          "name": "NASA",
          "orig": "en:NASA",
          "parents": [
            "Astronautics",
            "Aviation",
            "Applied sciences",
            "Space",
            "Aeronautics",
            "Transport",
            "Sciences",
            "Nature",
            "All topics",
            "Fundamental"
          ],
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        }
      ],
      "glosses": [
        "(used imitatively) A cliché used to exaggerate an accomplishment or milestone."
      ],
      "id": "en-one_small_step_for_man,_one_giant_leap_for_mankind-en-phrase-X5IaDCLL",
      "links": [
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        [
          "accomplishment",
          "accomplishment#English"
        ],
        [
          "milestone",
          "milestone#English"
        ]
      ],
      "raw_glosses": [
        "(idiomatic) (used imitatively) A cliché used to exaggerate an accomplishment or milestone."
      ],
      "tags": [
        "idiomatic"
      ],
      "wikipedia": [
        "Neil Armstrong"
      ]
    }
  ],
  "word": "one small step for man, one giant leap for mankind"
}

{
  "etymology_text": "Spoken by Neil Armstrong when he first stepped onto the surface of the Moon. Armstrong intended to say \"one small step for a man\", but misspoke.http://www.snopes.com/quotes/onesmall.asp",
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      "expansion": "one small step for man, one giant leap for mankind",
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    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "phrase",
  "senses": [
    {
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        "English allusions",
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        "en:NASA"
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      "glosses": [
        "(used imitatively) A cliché used to exaggerate an accomplishment or milestone."
      ],
      "links": [
        [
          "cliché",
          "cliché#English"
        ],
        [
          "accomplishment",
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        ],
        [
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        ]
      ],
      "raw_glosses": [
        "(idiomatic) (used imitatively) A cliché used to exaggerate an accomplishment or milestone."
      ],
      "tags": [
        "idiomatic"
      ],
      "wikipedia": [
        "Neil Armstrong"
      ]
    }
  ],
  "word": "one small step for man, one giant leap for mankind"
}