The Collaborative International Dictionary of English v.0.48:

Nibble \Nib"ble\, v. t. [imp. & p. p. Nibbled; p. pr. & vb. n.
   Nibbling.] [Cf. Nip.]
   To bite by little at a time; to seize gently with the mouth;
   to eat slowly or in small bits.
   [1913 Webster]

         Thy turfy mountains, where live nibbling sheep. --Shak.
   [1913 Webster]

Moby Thesaurus II by Grady Ward, 1.0:

45 Moby Thesaurus words for "nibbling":
   appetite, cannibalism, carnivorism, carnivority, carnivorousness,
   chewing, consumption, cropping, deglutition, devouring, devourment,
   dieting, dining, eating, epulation, feasting, feeding, gluttony,
   gobbling, grazing, herbivorism, herbivority, herbivorousness,
   hunger, ingestion, licking, manducation, mastication, messing,
   munching, nutrition, omnivorism, omnivorousness, omophagy,
   pantophagy, pasture, pasturing, pecking, regalement, relishing,
   rumination, savoring, tasting, vegetarianism, wolfing