It is a synonym, meaning "a noisy quarrel about something petty or trivial," according to Google Dictionary.
battle, debate, contend, quarrel, defend, question, agitate, disagree, discuss
An antonym means "opposite". So an antonym for the word synonym is antonym.
"bicker", "bickering", "brabble", "fuss", "niggle", "pettifog", "pettifoggery", "quibble", "spat" and "tiff"
Opposite.