Of considerable size, number, quantity, magnitude, or extent; large. See Synonyms at large. Of great force; strong: a big wind; in a big rage. Obsolete Of great strength. Mature or grown-up: big enough to take the bus by herself. Older or eldest. Used especially of a sibling: My big brother is leaving for college next week. Pregnant: big with child. Filled up; brimming over: felt big with love. Having or exercising considerable authority, control, or influence: a big official; a big chief. Conspicuous in position, wealth, or importance; prominent: a big figure in the peace movement. Of great significance; momentous: a big decision; a big victory. Informal Widely liked, used, or practiced; popular: "For public opinion . . . has grown harsh and yuppie-bashing is big\u201d ( Sally Jacobs). Informal Self-important; cocky: You're too big for your own good. Loud and firm; resounding: a big voice. Bountiful; generous: had a big heart. In a pretentious or boastful way: talked big about the new job. Informal With considerable success: made it big with their recent best-selling album. Informal In a thorough or unmistakable way; emphatically: failed big at the box office. big on Enthusiastic about; partial to: "The Japanese are big on ranking things and deciding which is Number One\u201d ( James Fallows).