WordNet (r) 3.0 (2006):

suggestible
    adj 1: susceptible or responsive to suggestion; "suggestible
           young minds"

Moby Thesaurus II by Grady Ward, 1.0:

23 Moby Thesaurus words for "suggestible":
   accessible, amenable, fictile, impressible, impressionable,
   influenceable, malleable, movable, open, open-minded, persuadable,
   persuasible, pervious, plastic, pliable, pliant, receptive,
   responsive, suasible, susceptible, susceptive, swayable, weak