prudish

adjective

Marked by excessive concern for propriety and good form: bluenosed, genteel, old-maidish, precise, priggish, prim, prissy, proper, puritanical, strait-laced, stuffy, Victorian. Idioms: prim and proper. See plain/fancy.

Definition: shy and strict in behavior
Antonyms: bold, brave, extroverted, liberal, outgoing, permissive

The adjective has one meaning:

Meaning #1: exaggeratedly proper
  Synonyms: priggish, prim, prissy, puritanical, square-toed, straitlaced, straightlaced, tight-laced, victorian