boil has 6 distinct synonyms spread across 4 of its 7 senses. Each sense below keeps its own list, because a synonym belongs to a meaning and not to a word: swapping one sense's substitute into another sense's sentence is how a thesaurus makes writing worse. Its one recorded opposite is freeze.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
come to the boiling point and change from a liquid to vapor
“Water boils at 100 degrees Celsius”
immerse or be immersed in a boiling liquid, often for cooking purposes
“boil potatoes”
Synonyms, antonyms and the broader and narrower relations for boil come from Princeton University’s WordNet. Full sources and licences.
be in an agitated emotional state
“The customer was seething with anger”
a painful sore with a hard core filled with pus
the temperature at which a liquid boils at sea level
“they brought the water to a boil”