Synonyms for Proper (same or very similar meaning)
WordNet sense 1 (no less than what is stated; worthy of the name):
real, real, real
WordNet sense 2 (exaggeratedly proper):
prudish
WordNet sense 3 (proper or legitimate):
kosher
WordNet sense 4 (in harmony with the spirit of particular persons or occasion):
fitting
WordNet sense 5 (in accord with accepted standards of usage or procedure):
correct, right
WordNet sense 6 (according with custom or propriety):
becoming, comely, decent, decorous
WordNet sense 7 ((sometimes followed by `to') applying to or characterized by or distinguishing something particular or special or unique):
specific
WordNet sense 8 (appropriate for a condition or purpose or occasion or a person's character, needs):
suitable, suited
WordNet sense 9 (suitable for a particular person or place or condition etc):
appropriate, appropriate
From the ODE community, based on WordNet
add/edit