Source : Webster's Revised Unabridged Dictionary (1913)

Credulous \Cred"u*lous\ (kr?d"?-l?s; 135), a. [L. credulus, fr.
   credere. See {Creed}.]
   1. Apt to believe on slight evidence; easily imposed upon;
      unsuspecting. --Landor.

            Eve, our credulous mother.            --Milton.

   2. Believed too readily. [Obs.] --Beau. & Fl.

Source : WordNet®

credulous
     adj 1: disposed to believe on little evidence; "the gimmick would
            convince none but the most credulous" [ant: {incredulous}]
     2: showing a lack of judgment or experience; "so credulous he
        believes everything he reads"