butt has 33 distinct synonyms spread across 9 of its 12 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. WordNet records no antonym for it — antonymy is a relation between word forms rather than concepts, so it is deliberately sparse.
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.
the part of a plant from which the roots spring or the part of a stalk or trunk nearest the roots
sports equipment consisting of an object set up for a marksman or archer to aim at
finely ground tobacco wrapped in paper; for smoking
a joint made by fastening ends together without overlapping
a large cask (especially one holding a volume equivalent to 2 hogsheads or 126 gallons)
the small unused part of something (especially the end of a cigarette that is left after smoking)
Synonyms, antonyms and the broader and narrower relations for butt come from Princeton University’s WordNet. Full sources and licences.
place end to end without overlapping
“The frames must be butted at the joints”