The Collaborative International Dictionary of English v.0.48:

Strait-jacket \Strait"-jack`et\, n.
   A dress of strong materials for restraining maniacs or those
   who are violently delirious. It has long sleeves, which are
   closed at the ends, confining the hands, and may be tied
   behind the back.
   [1913 Webster]

WordNet (r) 3.0 (2006):

straitjacket
    n 1: anything immaterial that severely hinders or confines;
         "they defected because Russian dance was in a
         straitjacket"; "the government is operating in an economic
         straitjacket"
    2: a garment similar to a jacket that is used to bind the arms
       tightly against the body as a means of restraining a violent
       person [syn: straitjacket, straightjacket]

Moby Thesaurus II by Grady Ward, 1.0:

61 Moby Thesaurus words for "straitjacket":
   Oregon boat, anchor, bilbo, bind, bond, bonds, bridle, camisole,
   chain, chains, collar, cuffs, enchain, entrammel, fasten, fetter,
   gag, gyve, gyves, halter, hamper, handcuff, handcuffs, hobble,
   hobbles, hog-tie, hopple, hopples, irons, lash, leading strings,
   leash, make fast, manacle, moor, muzzle, peg down, picket, pillory,
   pin down, pinion, put in irons, reins, restrain, restraint,
   restraints, rope, secure, shackle, stocks, straightjacket,
   strait-waistcoat, stranglehold, strap, tether, tie, tie down,
   tie up, trammel, trammels, yoke