1.Definition: not appropriate for a purpose or occasion

Related Adjective(s):wrong

2.Definition: not conforming to legality, moral law, or social convention

"Improper banking practices"

Related Adjective(s):unconventional, unlawful

3.Definition: not suitable or right or appropriate

"Slightly improper to dine alone with a married man", "Improper medication", "Improper attire for the golf course"