The Collaborative International Dictionary of English v.0.48:

Temperamental \Tem`per*a*men"tal\, a.
   Of or pertaining to temperament; constitutional. [R.] --Sir
   T. Browne.
   [1913 Webster]

WordNet (r) 3.0 (2006):

temperamental
    adj 1: relating to or caused by temperament; "temperamental
           indifference to neatness"; "temperamental peculiarities"
    2: subject to sharply varying moods; "a temperamental opera
       singer" [syn: moody, temperamental]
    3: likely to perform unpredictably; "erratic winds are the bane
       of a sailor"; "a temperamental motor; sometimes it would
       start and sometimes it wouldn't"; "that beautiful but
       temperamental instrument the flute"- Osbert Lancaster [syn:
       erratic, temperamental]

Moby Thesaurus II by Grady Ward, 1.0:

106 Moby Thesaurus words for "temperamental":
   affective, arbitrary, atavistic, bluff, bodily, born, brusque,
   capricious, changeable, characteristic, coeval, congenital,
   connatal, connate, connatural, constitutional, crabbed, crabby,
   cranky, crotchety, curt, dispositional, emotional, erratic,
   excitable, explosive, fanciful, fantasied, fantastic, fickle,
   flaky, freakish, genetic, grouchy, gruff, grumpy, harebrained,
   hereditary, high-strung, hot-blooded, hot-tempered, hotheaded,
   huffish, huffy, humorsome, hypersensitive, impatient, in the blood,
   inborn, inbred, incarnate, inconsistent, indigenous, inherited,
   innate, instinctive, instinctual, intellectual, irascible,
   irritable, kinky, maggoty, mental, mercurial, miffy, moody,
   motiveless, native, native to, natural, natural to, notional,
   organic, oversensitive, peevish, petulant, physical, prickly,
   primal, quirky, sensitive, short, short-tempered, snappish,
   spiritual, testy, tetchy, thin-skinned, ticklish, touchy,
   uncertain, undependable, uneven, unpredictable, unreasonable,
   unreliable, unrestrained, unstable, vagarious, vagrant, variable,
   volatile, wanton, waspish, wayward, whimsical