Bluff, blunt, brusque, curt, crusty, gruff mean abrupt and unceremonious in speech or manner.
Bluff, the only term of the group used in a complimentary sense, connotes outspokenness, rough good nature, and unconventionality which bespeak a sincerity that scorns the forms of politeness.
Blunt (see also DULL) implies such directness and plain speaking as to suggest lack of consideration for the feelings of others and some disregard for the amenities of life.
Brusque suggests a certain sharpness of manner and ungraciousness of speech.
Curt implies disconcerting shortness or rude conciseness.
Crusty implies a forbidding exterior and a manner marked by asperity or acerbity that sometimes belies real kindness of heart.
Gruff carries a stronger implication of surliness and roughness than crusty and distinctively suggests curt and hoarse or guttural utterance but like the former may suggest an underlying kindliness.