Synonyms for Forgetful (same or very similar meaning)
WordNet sense 1 ((of memory) deficient in retentiveness or range):
short, unretentiveWordNet sense 2 (not mindful or attentive):
mindless, unmindfulWordNet sense 3 (failing to keep in mind):
obliviousWordNet sense 4 (showing a lack of attention or care):
inattentiveFrom the ODE community, based on WordNetadd/edit