An inseparable verbal prefix or particle. It is prefixed:
(a) To verbs to express the contrary, and not the simple negative, of the action of the verb to which it is prefixed; as in
unbend,
uncoil,
undo,
unfold.
(b) To nouns to form verbs expressing privation of the thing, quality, or state expressed by the noun, or separation from it; as in
unchild,
unsex. Sometimes particles and participial adjectives formed with this prefix coincide in form with compounds of the negative prefix
un- (see 2d
Un-); as in
undone (from
undo), meaning unfastened, ruined; and
undone (from 2d
un- and
done) meaning not done, not finished.
Un- is sometimes used with an intensive force merely; as in
unloose. [
1913 Webster]
" Compounds of this prefix are given in full in their proper order in the Vocabulary."
[1913 Webster]