The Collaborative International Dictionary of English v.0.48:

Quirky \Quirk"y\ (kw[~e]rk"[y^]), a.
   Full of quirks; tricky; as, a quirky lawyer.
   [1913 Webster]

WordNet (r) 3.0 (2006):

quirky
    adj 1: informal terms; strikingly unconventional [syn: far-
           out, kinky, offbeat, quirky, way-out]

Moby Thesaurus II by Grady Ward, 1.0:

56 Moby Thesaurus words for "quirky":
   abnormal, anomalous, arbitrary, capricious, crank, crankish,
   cranky, crotchety, deviant, deviative, different, divergent, dotty,
   eccentric, erratic, exceptional, fanciful, fantasied, fantastic,
   fey, flaky, freakish, funny, harebrained, humorsome, idiocratic,
   idiosyncratic, irregular, kinky, kooky, maggoty, moody, motiveless,
   notional, nutty, odd, oddball, peculiar, petulant, queer,
   screwball, screwy, singular, strange, temperamental, twisted,
   unconventional, unnatural, unreasonable, unrestrained, vagarious,
   vagrant, wacky, wanton, wayward, whimsical