Cos'è bad? Cos'è bad? Not achieving an adequate standard; poor: a bad concert. Evil; sinful.Vulgar or obscene: bad language. Informal Disobedient or naughty: bad children. Disagreeable, unpleasant, or disturbing: a bad piece of news. Unfavorable: bad reviews for the play. Not fresh; rotten or spoiled: bad meat. Injurious in effect; detrimental: bad habits. Not working properly; defective: a bad telephone connection. Full of or exhibiting faults or errors: bad grammar. Having no validity; void: passed bad checks. Being so far behind in repayment as to be considered a loss: bad loans. Severe; intense: a bad cold. Being in poor health or in pain: I feel bad today. Being in poor condition; diseased: bad lungs. Sorry; regretful: She feels bad about how she treated you. Slang Very good; great.Something that is below standard or expectations, as of ethics or decency: weighing the good against the bad. Usage Problem Badly.in bad Informal In trouble or disfavor.my bad Slang Used to acknowledge that one is at fault.half Informal Reasonably good.Archaic A past tense of bid.