WordNet (r) 3.0 (2006):

straightlaced
    adj 1: exaggeratedly proper; "my straitlaced Aunt Anna doesn't
           approve of my miniskirts" [syn: priggish, prim,
           prissy, prudish, puritanical, square-toed,
           straitlaced, strait-laced, straightlaced,
           straight-laced, tight-laced, victorian]

Moby Thesaurus II by Grady Ward, 1.0:

34 Moby Thesaurus words for "straightlaced":
   dour, firm, fundamentalist, hard, hidebound, impliable, inexorable,
   inflexible, iron, ironbound, ironclad, ironhanded, muscle-bound,
   obdurate, obstinate, orthodox, procrustean, purist, puristic,
   puritan, puritanic, relentless, rigid, rigorist, rigoristic,
   rigorous, rockbound, stiff, straitlaced, stubborn, unbending,
   uncompromising, unrelenting, unyielding