adjective
- not proper; not strictly belonging, applicable, correct, etc.; erroneous: He drew improper conclusions from the scant evidence.
- not in accordance with propriety of behavior, manners, etc.: improper conduct at a funeral.
- unsuitable or inappropriate, as for the purpose or occasion: improper attire for a formal dance.
- abnormal or irregular: improper functioning of the speech mechanism.
adjective
- lacking propriety; not seemly or fitting
- unsuitable for a certain use or occasion; inappropriatean improper use for a tool
- irregular or abnormal
mid-15c., “not true,” from French impropre (14c.), from Latin improprius, from assimilated form of in- “not, opposite of” (see in- (1)) + proprius (see proper). Meaning “not suited, unfit” is from 1560s; that of “not in accordance with good manners, modesty, decency” is from 1739. Related: Improperly (late 14c.).