dissonant

1. Harsh and inharmonious in sound; discordant.
2. Being at variance; disagreeing.
3. Music. Constituting or producing a dissonance.

[Middle English dissonaunt, from Old French dissonant, from Latin dissonāns, dissonant-, present participle of dissonāre, to be dissonant : dis-, apart; see dis- + sonāre, to sound.]

adjective

1. Characterized by unpleasant discordance of sound: cacophonous, discordant, disharmonious, inharmonic, inharmonious, rude, unharmonious, unmusical. See agree/disagree, sounds/pleasant sounds/unpleasant sounds/neutral sounds or silence.
2. Made up of parts or qualities that are disparate or otherwise markedly lacking in consistency: discordant, discrepant, incompatible, incongruent, incongruous, inconsistent. See agree/disagree.

Definition: different, conflicting
Antonyms: coinciding, compatible, complementary, consonant, similar

adj

Definition: unharmonious
Antonyms: concordant, harmonious

The adjective has 3 meanings:

Meaning #1: not musical in nature
  Synonyms: unmusical, nonmusical

Meaning #2: (music) characterized by musical dissonance; harmonically unresolved
  Synonym: unresolved

Meaning #3: lacking in harmony
  Synonyms: discordant, disharmonious, inharmonic