WordNet sense 1 (not in keeping with accepted standards of what is right or proper in polite society):

indecorous, unbecoming, unseemly, untoward, uncomely

WordNet sense 2 (not suitable or right or appropriate):

improper

WordNet sense 3 (offending against sexual mores in conduct or appearance):

immodest

WordNet sense 4 (designed to incite to indecency or lust):

obscene

WordNet sense 5 (verging on the indecent):

indelicate

WordNet sense 6 (conspicuously and tastelessly indecent):

coarse, crude, gross