to speak unfavourably and off-puttingly of (something or someone)
unsell in American English
(unˈsel)
transitive verbWord forms: -sold, -selling
to dissuade from a belief in the desirability, value, wisdom, or truth of something
He tried to unsell the public on its faith in rearmament
Word origin
[1925–30; un-2 + sell1]This word is first recorded in the period 1925–30. Other words that entered Englishat around the same time include: distinctive feature, dropout, gimmick, off-line, payloadun- is a prefix freely used in English to form verbs expressing a reversal of some actionor state, or removal, deprivation, release, etc. (unbend; uncork; unfasten; etc.), or to intensify the force of a verb already having such a meaning (unloose)