| brush down | | | |
| brush off | | | |
| brush up | | | |
| bubble over | | | |
| bucket down | | | |
| bucket list | | | |
| bucket of bolts | | | |
| bucket of rust | | | |
| bucket of syrup | | | |
| buck fever | | | |
| buck for | | | |
| buckle down | | | |
| buckle to | | | |
| buckle up | | | |
| Buckley's and none | | | |
| Buckley's chance | | | |
| buck-passing | | | |
| buck the trend | | | |
| buck up | | | |
| buck up one's ideas | | | |
| buff out | | | |
| buff the muffin | | | |
| buff up | | | |
| bugger off | | | |
| Buggins's turn | | | |
| bug off | | | |
| bug storm | | | |
| build a better mousetrap | | | |
| build a case | | | |
| build bridges | | | |
| build castles in the air | | | |
| build character | | | |
| build on sand | | | |
| build the plane while flying it | | | |
| build up | | | |
| built different | | | |
| built like a brick outhouse | | | |
| built like a brick shipyard | | | |
| built like a brick shithouse | | | |
| bulk billing | | | |
| bull in a china shop | | | |
| bull session | | | |
| Bumfuck, Egypt | | | |
| bump and grind | | | |
| bumper crop | | | |
| bump in the road | | | |
| bump into | | | |
| bump off | | | |
| bump up | | | |
| bum rap | | | |
| bum rush | | | |
| bum's rush | | | |
| bum steer | | | |
| bundle of energy | | | |
| bundle off | | | |
| bundle of joy | | | |
| bundle of laughs | | | |
| bundle of nerves | | | |
| bun fight | | | |
| bunker | | | |
| bunny hop | | | |
| bunny hug | | | |
| buoy up | | | |
| buried treasure | | | |
| burn a hole in someone's pocket | | | |
| burn bread | | | |
| burn daylight | | | |
| burning question | | | |
| burn one's bridges | | | |
| burn one's fingers | | | |
| burn out | | | |
| burn rubber | | | |
| burn someone's ears | | | |
| burn that bridge when one comes to it | | | |
| burn the candle at both ends | | | |
| burn the midnight oil | | | |
| burn the roof | | | |
| burn time | | | |
| burr in one's saddle | | | |
| burst in | | | |
| burst into tears | | | |
| burst out laughing | | | |
| burst someone's bubble | | | |
| bury one's head in the sand | | | |
| bury the hatchet | | | |
| bury the lede | | | |
| bush league | | | |
| bush telegraph | | | |
| business as usual | | | |
| business end | | | |
| business girl | | | |
| busman's holiday | | | |
| bus plunge | | | |
| bust a cap | | | |
| bust a move | | | |
| bust a nut | | | |
| bust ass | | | |
| bust chops | | | |
| busted flush | | | |
| bust on | | | |