adjective

open, honest, and direct in speech or writing, especially when dealing with unpalatable matters.

a long and frank discussion

candid,direct,forthright,plain,plain-spoken,straight,straightforward,straight from the shoulder,explicit,unequivocal,unambiguous,unvarnished,bald,to the point,no-nonsense,matter-of-fact,open,honest,truthful,sincere,guileless,artless,outspoken,bluff,blunt,brutal,unsparing,upfront,warts and all,on the level,on the up and up,round,free-spoken