A must is something that's so important it can't be missed or ignored. When you're taking kayaking lessons, a lifejacket is a must.

Anything that is required is a must: drinking enough water is a must for being healthy. When you adopt a new dog, making sure he'll get along with your cat is a must. Another meaning of the noun must is a stale, stuffy smell. Your damp basement and dry, hot attic might both smell of must. This meaning comes from the adjective musty, a variation on the older, now obsolete moisty.

Definitions of must
  1. noun
    a necessary or essential thing
    “seat belts are an absolute must
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    type of:
    essential, necessary, necessity, requirement, requisite
    anything indispensable
  2. adjective
    highly recommended
    “a book that is must reading”
    basic and fundamental
  3. noun
    the quality of smelling or tasting old or stale or mouldy
    synonyms: moldiness, mustiness
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    type of:
    having lost purity and freshness as a consequence of aging
  4. noun
    grape juice before or during fermentation
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    type of:
    grape juice
    the juice of grapes
Word Family

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