The Collaborative International Dictionary of English v.0.48:
Unsufferable \Un*suf"fer*a*ble\, a. Insufferable. [Obs.] --Hooker. -- Un*suf"fer*a*bly, adv. [Obs.] [1913 Webster]WordNet (r) 3.0 (2006):
unsufferable adj 1: used of persons or their behavior; "impossible behavior"; "insufferable insolence" [syn: impossible, insufferable, unacceptable, unsufferable]