of poor quality or a low standard

a bad diet

bad eyesight

not such as to be hoped for or desired; unpleasant or unwelcome

bad news

it was the worst day of his life

bad luck

failing to conform to standards of moral virtue or acceptable conduct

the bad guys

bad behaviour

(of a part of the body) injured, diseased, or painful

a bad back

(of food) decayed; putrid

everything in the fridge went bad

regretful, guilty, or ashamed about something

she feels bad about ending their engagement

I feel bad that our business is benefiting from something so horrible

worthless; not valid

he ran up 87 bad cheques

good; excellent

they want the baddest, best-looking Corvette there is

badly

my knee for some reason just swelled up real bad