Noah Webster's New International Dictionary of the English Language

1. (a.) Not proper; not appropriate; not fitted to the circumstances, design, or end; unfit; not becoming; incongruous; inappropriate; indecent; as, an improper medicine; improper thought, behavior, language, dress.

2. (a.) Not peculiar or appropriate to individuals; general; common.

3. (a.) Not according to facts; inaccurate; erroneous.

4. (v. t.) To appropriate; to limit.