Open English Wordnet
Adjectives
(a)impropernot suitable or right or appropriate“slightly improper to dine alone with a married man”,
“improper medication”,
“improper attire for the golf course” (s)improper, unconventional, unlawfulnot conforming to legality, moral law, or social convention“an unconventional marriage”,
“improper banking practices” (s)improper, wrongnot appropriate for a purpose or occasion“said all the wrong things”