but / butt are similar-sounding terms with different meanings (referred to as homophones). To better understand the differences, see below for definitions, pronunciation guides, and example sentences using each term. 👇
but: NA
butt: (noun) thick end of the handle. (noun) the part of a plant from which the roots spring or the part of a stalk or trunk nearest the roots. (noun) a victim of ridicule or pranks. (noun) a large cask (especially one holding a volume equivalent to 2 hogsheads or 126 gallons). (noun) the small unused part of something (especially the end of a cigarette that is left after smoking). (verb) to strike, thrust or shove against. (verb) place end to end without overlapping.
but: b·AH·t
butt: b·AH·t
(Examples are Wikipedia snippets under the CC ShareAlike 3.0 license. Definitions drawn from WordNet.)