bad

Concise Oxford English Dictionary © 2008 Oxford University Press:
bad/bad/

▶adjective (worse, worst)

• 1 of poor quality or a low standard.

  ■ (often bad at) not able to do a particular thing well.

  ■ inappropriate.

• 2 unwelcome or unpleasant.

  ■ severe or serious.

  ■ (bad for) harmful to.

• 3 offending moral standards or accepted conventions.

• 4 injured, ill, or diseased.

• 5 (of food) decayed.

• 6 guilty; ashamed.

• 7 (badder, baddest) informal, chiefly N. Amer. good; excellent.

– phrases
be bad news informal be unwelcome or unpleasant.
in a bad way ill or in trouble.
to the bad

• 1 to ruin.

• 2 in deficit.

too bad informal indicating that something is regrettable but now beyond retrieval.

– derivatives
baddish adjective,
badness noun.

– origin ME: perh. from OE bǣddel ‘hermaphrodite, womanish man’.