Definition of "Bad" :
noun: that which is below standard or expectations as of ethics or decency
"Take the bad with the good."
adjective: feeling physical discomfort or pain (tough' is occasionally used colloquially for bad')
"My throat feels bad."
adjective: (of foodstuffs) not in an edible or usable condition
adjective: not working properly
"A bad telephone connection."
adjective: reproduced fraudulently
"Like a bad penny...."
adjective: having undesirable or negative qualities
"A bad report card."
adjective: characterized by wickedness or immorality
"Led a very bad life."
adjective: feeling or expressing regret or sorrow or a sense of loss over something done or undone
"He felt bad about breaking the vase."
adjective: capable of harming
adjective: physically unsound or diseased
"Has a bad back."
adjective: very intense
"A bad headache."
adjective: not financially safe or secure
"A bad investment."
"So-called bad grammar."
adjective: below average in quality or performance
"A bad chess player."
adjective: not capable of being collected
"A bad (or uncollectible) debt."
adverb: very much; strongly
"I wanted it badly enough to work hard for it."
adverb: with great intensity (bad' is a nonstandard variant for badly')
"The injury hurt badly."