Main Entry: ¹but·ton

Pronunciation: \ˈbə-t^ən\

Function: noun

Usage: often attributive

Etymology: Middle English boton, from Anglo-French butun rose hip, stud, from buter to thrust — more at butt

Date: 14th century

1 a : a small knob or disk secured to an article (as of clothing) and used as a fastener by passing it through a buttonhole or loop b : a usually circular metal or plastic badge bearing a stamped design or printed slogan <campaign button>
2 : something that resembles a button: as a : any of various parts or growths of a plant or of an animal: as (1) : bud (2) : an immature whole mushroom; especially : button mushroom (3) : the terminal segment of a rattlesnake's rattle b : a small globule of metal remaining after fusion (as in assaying) c : a guard on the tip of a fencing foil
3 a : push button b : something (as a push button) that has the real or symbolic capability of initiating a catastrophe (as a nuclear attack) <has his finger on the button> c : a hidden sensitivity that can be manipulated to produce a desired response <knows how to push my buttons> d : a usually box-shaped computer icon that initiates a specific software function
4 : the point of the chin especially as a target for a knockout blow

— but·ton·less \-ləs\ adjective

— on the button : exactly <arrived at noon on the button>; also : exactly on target : on the nose <the estimate was right on the button>