WordNet (r) 3.0 (2006):

uncomprehending
    adj 1: lacking understanding; "tried to explain to her
           uncomprehending husband"

Moby Thesaurus II by Grady Ward, 1.0:

51 Moby Thesaurus words for "uncomprehending":
   awkward, blankminded, blind, blindfold, blindfolded, callow,
   dim-sighted, dumb, empty, empty-headed, gauche, green, groping,
   ignorant, imperceptive, impercipient, inane, inexperienced,
   innocent, insensible, know-nothing, mind-blind, myopic, naive,
   nearsighted, nescient, nonunderstanding, purblind, raw,
   shortsighted, simple, strange to, tentative, unacquainted,
   unapprehending, unapprized, unconversant, undiscerning,
   unenlightened, unfamiliar, unilluminated, uninformed, uninitiated,
   unintelligent, unknowing, unperceptive, unposted, unripe, unsure,
   unversed, vacuous