RhymeZone: unproper definitions

Definitions of unproper:

adjective: (obsolete) Improper, not according with fact or reason; wrong, irregular.
adjective: (now rare) Improper, not suited for its use or application; inappropriate.
adjective: (obsolete) Not belonging to a given person; someone else's.
adjective: (rare) Improper, not according with good standards of behaviour; indecent, indecorous.

(Definitions from Wiktionary)