butt against vs butt on

butt against and butt on both are verbs.

Word	Noun	Adjective	Verb	Adverb
butt against	No	No	Yes	No
butt on	No	No	Yes	No

As verbs, butt against and butt on are synonyms defined as:

Other synonyms of butt against include abut, adjoin, border, butt, edge, march.

butt against (verb)	butt on (verb)
lie adjacent to another or share a boundary	lie adjacent to another or share a boundary
collide violently with an obstacle