butt3

noun

• 1 (also butt end) the thicker end of something, especially a tool or a weapon:a rifle butt
• the square end of a plank or plate meeting the end or side of another, as in the side of a ship: [as modifier]:a butt joint
• the thicker or hind end of a hide used for leather.

• 2 (also butt end) the stub of a cigar or a cigarette.

• 3 informal, chiefly North American a person’s buttocks or anus: I was being paid to sit on my butt and watch television

• 4the trunk of a tree, especially the part just above the ground.

verb

• adjoin or meet end to end:the shop butted up against the row of houses
• [with object] join (pieces of stone, timber, and other building materials) with the ends or sides flat against each other.