Un

pronoun, Dialect.
1.
one:
young uns; He’s a bad un.
1.
United Nations (def 1).
1.
a prefix meaning “not,” freely used as an English formative, giving negative or opposite force in adjectives and their derivative adverbs and nouns (unfair; unfairly; unfairness; unfelt; unseen; unfitting; unformed; unheard-of; un-get-at-able), and less freely used in certain other nouns (unrest; unemployment).
1.
a prefix freely used in English to form verbs expressing a reversal of some action or state, or removal, deprivation, release, etc. (unbend; uncork; unfasten , etc.), or to intensify the force of a verb already having such a meaning (unloose).
abbreviation
1.
United Nations
prefix
1.
(freely used with adjectives, participles, and their derivative adverbs and nouns: less frequently used with certain other nouns) not; contrary to; opposite of: uncertain, uncomplaining, unemotionally, untidiness, unbelief, unrest, untruth
prefix
1.
denoting reversal of an action or state: uncover, untangle
2.
denoting removal from, release, or deprivation: unharness, unman, unthrone
3.
(intensifier): unloose

un- 1
pref.
Not: unmyelinated.
un
unit
UN
1.
United Nations
2.
until (shortwave transmission)