From The Collaborative International Dictionary of English v.0.48 :
Gullible \Gul"li*ble\, a.
Easily gulled; that may be duped. -- Gul"li*bii`i*ty, n.
--Burke.
[1913 Webster]
From WordNet (r) 3.0 (2006) :
gullible
adj 1: naive and easily deceived or tricked; "at that early age
she had been gullible and in love" [syn: fleeceable,
green, gullible]
2: easily tricked because of being too trusting; "gullible
tourists taken in by the shell game"
From Moby Thesaurus II by Grady Ward, 1.0 :
31 Moby Thesaurus words for "gullible":
artless, befoolable, born yesterday, credulous, cullible,
deceivable, deludable, dupable, easy, exploitable, foolable, green,
hoaxable, hoodwinkable, humbugable, immature, inexperienced,
ingenuous, innocent, naive, persuadable, seduceable, simple, soft,
susceptible, unsophisticated, unsuspecting, unsuspicious, unwary,
victimizable, wide-eyed