Antonyms of adj improper

3 senses of improper

Sense 1
improper (vs. proper) -- (not suitable or right or appropriate; "slightly improper to dine alone with a married man"; "improper medication"; "improper attire for the golf course")

proper (vs. improper) -- (marked by suitability or rightness or appropriateness; "proper medical treatment"; "proper manners")
        => becoming, comely, comme il faut, decent, decorous, seemly -- (according with custom or propriety; "her becoming modesty"; "comely behavior"; "it is not comme il faut for a gentleman to be constantly asking for money"; "a decent burial"; "seemly behavior")
        => correct, right -- (socially right or correct; "it isn't right to leave the party without saying goodbye"; "correct behavior")
        => correct, right -- (in accord with accepted standards of usage or procedure; "what's the right word for this?"; "the right way to open oysters")
        => fitting -- (in harmony with the spirit of particular persons or occasion; "We have come to dedicate a portion of that field...It is altogether fitting and proper that we should do this")
        => halal -- (proper or legitimate; "the fund earns halal profits in full compliance with the Shari'a")
        => kosher -- (proper or legitimate)
        => priggish, prim, prissy, prudish, puritanical, square-toed, straitlaced, strait-laced, straightlaced, straight-laced, tight-laced, victorian -- (exaggeratedly proper; "my straitlaced Aunt Anna doesn't approve of my miniskirts")

Sense 2
improper, unconventional, unlawful -- (not conforming to legality, moral law, or social convention; "an unconventional marriage"; "improper banking practices")

INDIRECT (VIA irregular) -> regular -- (in accordance with fixed order or procedure or principle; "his regular calls on his customers"; "regular meals"; "regular duties")

Sense 3
improper, wrong -- (not appropriate for a purpose or occasion; "said all the wrong things")

INDIRECT (VIA inappropriate) -> appropriate -- (suitable for a particular person or place or condition etc; "a book not appropriate for children"; "a funeral conducted the appropriate solemnity"; "it seems that an apology is appropriate")

Similarity of adj improper

3 senses of improper

Sense 1
improper (vs. proper) -- (not suitable or right or appropriate; "slightly improper to dine alone with a married man"; "improper medication"; "improper attire for the golf course")
       => indecent, indecorous, unbecoming, uncomely, unseemly, untoward -- (not in keeping with accepted standards of what is right or proper in polite society; "was buried with indecent haste"; "indecorous behavior"; "language unbecoming to a lady"; "unseemly to use profanity"; "moved to curb their untoward ribaldry")
       => out-of-the-way -- (improper or even offensive; "out-of-the-way remarks")
       => wrong, incorrect -- (not in accord with established usage or procedure; "the wrong medicine"; "the wrong way to shuck clams"; "it is incorrect for a policeman to accept gifts")
          Also See-> inappropriate#1; indecent#2; indecorous#1, indelicate#2; unfit#1; wrong#2

Sense 2
improper, unconventional, unlawful -- (not conforming to legality, moral law, or social convention; "an unconventional marriage"; "improper banking practices")
       => irregular (vs. regular) -- (contrary to rule or accepted order or general practice; "irregular hiring practices")

Sense 3
improper, wrong -- (not appropriate for a purpose or occasion; "said all the wrong things")
       => inappropriate (vs. appropriate) -- (not suitable for a particular occasion etc; "noise seems inappropriate at a time of sadness"; "inappropriate shoes for a walk on the beach"; "put inappropriate pressure on them")