A generally disk-shaped fastener used to join two parts of a garment by fitting through a buttonhole or loop. Such an object used for decoration. Any of various objects resembling a button, especially: A push-button switch. The blunt tip of a fencing foil. A fused metal or glass globule. Computer Science In graphical user interface systems, a well-defined area within the interface that is clicked to select a command. Computer Science In a hypertext database, an icon that when selected allows a user to view a particular associated object. Any of various knoblike structures of a plant or animal, especially: An immature, unexpanded mushroom. The tip of a rattlesnake's rattle. A usually round flat badge that bears a design or printed information and is typically pinned to a garment: a campaign button. Informal The end of the chin, regarded as the point of impact for a punch. To fasten with buttons: buttoned his shirt; buttoned up her raincoat. To decorate or furnish with buttons. Informal To close (the lips or mouth): Button your lip. To be or be capable of being fastened with buttons: The blouse buttons up the back. button up To fasten one's clothing tightly, as against cold weather. button up To close or seal securely: button up the cabin for winter. button up To complete the final details of: "Publication is a couple of months off; they're just buttoning up paperback rights\u201d ( Donald Dale Jackson). on the button Exactly; precisely.