Dictionary:

cacophonous

  (kə-kŏf'ə-nəs)

Having a harsh, unpleasant sound; discordant.

[From Greek kakophōnos : kakos, bad + phōnē, sound.]

adjective

Characterized by unpleasant discordance of sound: discordant, disharmonious, dissonant, inharmonic, inharmonious, rude, unharmonious, unmusical. See agree/disagree, sounds/pleasant sounds/unpleasant sounds/neutral sounds or silence.

Definition: harsh sounding
Antonyms: quiet

The adjective has one meaning:

Meaning #1: having an unpleasant sound
  Synonym: cacophonic
  Antonym: euphonious (meaning #1)