Im‐prop″er (?), a. [F. impropre, L. improprius; pref. im- not + proprius proper. See Proper.] 1. Not proper; not suitable; not fitted to the circumstances, design, or end; unfit; not becoming; incongruous; inappropriate; indecent; as, an improper medicine; improper thought, behavior, language, dress.
Follow'd his enemy king, and did him service,
Improper for a slave. Shak.
And to their proper operation still,
Ascribe all Good; to their improper, Ill. Pope.
2. Not peculiar or appropriate to individuals; general; common.
Not to be adorned with any art but such improper ones as nature is said to bestow, as singing and poetry. J. Fletcher.
3. Not according to facts; inaccurate; erroneous.
Improper diphthong. See under Diphthong. — Improper feud, an original feud, not earned by military service. Mozley & W. — Improper fraction. See under Fraction.