The Collaborative International Dictionary of English v.0.48:

Suspender \Sus*pend"er\, n.
   One who, or that which, suspends; esp., one of a pair of
   straps or braces worn over the shoulders, for holding up the
   trousers.
   [1913 Webster]

WordNet (r) 3.0 (2006):

suspender
    n 1: elastic straps that hold trousers up (usually used in the
         plural) [syn: brace, suspender, gallus]

Moby Thesaurus II by Grady Ward, 1.0:

29 Moby Thesaurus words for "suspender":
   bar, belt, boom, braces, button, clotheshorse, clothespin, crane,
   gallows, galluses, garter, gibbet, hake, hanger, hook, horse, knob,
   nail, pair of suspenders, peg, pothook, ring, spar, stud,
   supporter, suspenders, suspensory, yard, yardarm



Bouvier's Law Dictionary, Revised 6th Ed (1856):

SUSPENDER, Scotch law. He in whose favor a suspension is made.
     2. In general a suspender is required to give caution to pay the debt
in the event it shall be found due. Where the suspender cannot, from his low
or suspected circumstances, procure unquestionable security, the lords admit
juratory caution; but the reasons of suspension are in that case, to be
considered with particular accuracy at passing the bill. Act. S. 8 Nov.
1682; Ersk. Prin. L. Scot. 4, 3, 6.