The Collaborative International Dictionary of English v.0.48:

Strait-laced \Strait"-laced`\, a.
   1. Bound with stays.
      [1913 Webster]

            Let nature have scope to fashion the body as she
            thinks best; we have few well-shaped that are
            strait-laced.                         --Locke.
      [1913 Webster]

   2. Restricted; stiff; constrained. [R.] --Fuller.
      [1913 Webster]

   3. Rigid in opinion; strict in manners or morals.
      [1913 Webster]

WordNet (r) 3.0 (2006):

strait-laced
    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:

98 Moby Thesaurus words for "straitlaced":
   Quakerish, Sabbatarian, Victorian, authoritarian, bigot, bigoted,
   borne, censorious, closed, constricted, cramped, creedbound, deaf,
   deaf to reason, demure, dogmatic, dour, evangelical, fanatical,
   firm, fundamentalist, genteel, hard, hidebound, hyperorthodox,
   illiberal, impliable, inexorable, inflexible, insular, iron,
   ironbound, ironclad, ironhanded, libertine, literalist,
   literalistic, little, little-minded, mean, mean-minded,
   mean-spirited, mid-Victorian, muscle-bound, narrow, narrow-hearted,
   narrow-minded, narrow-souled, narrow-spirited, nearsighted,
   obdurate, obstinate, old-maidish, orthodox, overmodest, parochial,
   petty, precisianist, precisianistic, prig, priggish, prim, prissy,
   procrustean, provincial, prudish, purblind, purist, puristic,
   puritan, puritanic, puritanical, relentless, rigid, rigorist,
   rigoristic, rigorous, rockbound, sanctimonious, shortsighted,
   small, small-minded, smug, staunch, stiff, stiff-necked,
   straightlaced, strict, stubborn, stuffy, unbending, uncatholic,
   uncharitable, uncompromising, ungenerous, unliberal, unrelenting,
   unyielding