Synonyms of improper in English:

improper


See definition of improper

adjective

1‘it was improper for policemen to accept gifts’

SYNONYMS
inappropriate, unacceptable, unsuitable, unprofessional, irregular, illegitimate, against the rules
unethical, corrupt, immoral, dishonest, dishonourable, unscrupulous
informal crooked, not cricket
ANTONYMS

acceptable, proper

2‘it would have been thought improper for two young ladies to drive a young man home’

SYNONYMS
unseemly, indecorous, unbecoming, unfitting, out of keeping, unladylike, ungentlemanly, indiscreet, indelicate, impolite, undignified
indecent, unwholesome, immodest, immoral
outrageous, scandalous, shocking, offensive, distasteful
forward, bold, brazen, shameless
informal fresh, cheeky
ANTONYMS

proper

3‘he recited an extremely improper poem’

SYNONYMS
indecent, risqué, off colour, indelicate, suggestive, naughty, ribald, earthy, Rabelaisian, smutty, dirty, filthy, vulgar, crude, rude, obscene, lewd, pornographic
informal blue, raunchy, steamy, near the bone, near the knuckle, nudge-nudge
British informal fruity, saucy
ANTONYMS

decent