a small disk, knob, or the like for sewing or otherwise attaching to an article, as of clothing, serving as a fastening when passed through a buttonhole or loop.

anything resembling a button, esp. in being small and round, as any of various candies, ornaments, tags, identification badges, reflectors, markers, etc.

a badge or emblem bearing a name, slogan, identifying figure, etc., for wear on the lapel, dress, etc.

campaign buttons.

any small knob or disk pressed to activate an electric circuit, release a spring, or otherwise operate or open a machine, small door, toy, etc.

Botany . a bud or other protuberant part of a plant.

Mycology .

a young or undeveloped mushroom.

any protuberant part of a fungus.

Zoology . any of various small parts or structures resembling a button, as the rattle at the tip of the tail in a very young rattlesnake.

Boxing Informal . the point of the chin.

Also called turn button. a fastener for a door, window, etc., having two arms and rotating on a pivot that is attached to the frame.

Metallurgy . (in assaying) a small globule or lump of metal at the bottom of a crucible after fusion.

Fencing . the protective, blunting knob fixed to the point of a foil.

Horology . crown ( def. 19 ) .

Computers . (in a graphical user interface) any of the small, labeled areas upon which the user can click with a mouse to choose an option.

to fasten with a button or buttons

She quickly buttoned her coat.

to insert (a button) in a buttonhole or loop

He buttoned the top button of his shirt.

to provide (something) with a button or buttons.

to be capable of being buttoned

This coat buttons, but that one zips.

button up

Informal .

Also, button one's lip. to become or keep silent.

to fasten securely; close up

Within a short time, everything on the submarine was buttoned up.

to fasten fully or put on, esp. an outer garment

Button up before going out.

to complete successfully; finish

The report is all buttoned up.

have all one's buttons, Informal . to be mentally competent, alert

and sane; have all one's wits

At 106 she still has all her buttons.

on the button, Informal . exactly as desired, expected, specified

etc.

The prediction for snow was right on the button.

noun

catch , clasp , fastening , frog , knob , stud , adjuster , dial , on/off , power switch , switch , toggle , tuner , badge , bauble , buckle , bud , chin , emblem , fasten , fastener , hook , pearl