Wiktionary
n. (label en set phrase) aggressive remarks that foreseeably may lead to a potentially violent confrontation; in law, often considered mitigation for otherwise sanctionable behavior (fighting).
Wikipedia
Fighting words are written or spoken words, generally expressed to incite hatred or violence from their target. Specific definitions, freedoms, and limitations of fighting words vary by jurisdiction. It is also used in a general sense of words that when uttered tend to create (deliberately or not) a verbal or physical confrontation by their mere usage.
Fighting Words is a Canadian panel quiz television series which aired on CBC Television from 1952 to 1962. The series returned for short runs in 1970 and 1982.
Usage examples of "fighting words".
They were exchanging fighting words, but what the trouble was about Gillian never knew.
Artor needs young men to save the Seneschal, Gilbert thought, his eyes expressionless, not old men afraid of fighting words and deeds.
For every nation and for every race there are fighting words - and when a race is so notoriously emotionally unstable as the Hallichek such words may be relied upon to start a fight.
These would have been fighting words from almost anybody but Sourdough.