| bust one's balls | | | |
| bust one's butt | | | |
| bust one's chops | | | |
| bust the dust | | | |
| busy as a bee | | | |
| busy as a nailer | | | |
| busy work | | | |
| butcher's bill | | | |
| butcher's thumb | | | |
| but good | | | |
| but seriously folks | | | |
| butter face | | | |
| butterfingers | | | |
| butterfly upon a wheel | | | |
| butter one's bread on both sides | | | |
| butter the cony | | | |
| butter wouldn't melt in someone's mouth | | | |
| butt heads | | | |
| but then | | | |
| butt in | | | |
| button-down | | | |
| buttoned-down | | | |
| button nose | | | |
| button one's lip | | | |
| button pusher | | | |
| butt up | | | |
| buy a dog and bark oneself | | | |
| buy and hold | | | |
| buy a ticket to | | | |
| buy into | | | |
| buy it | | | |
| buy out | | | |
| buy straw hats in winter | | | |
| buy the farm | | | |
| buy time | | | |
| buy to let | | | |
| buy up | | | |
| buzzer-beater | | | |
| buzzkill | | | |
| buzz off | | | |
| by a hair's breadth | | | |
| by a landslide | | | |
| by all accounts | | | |
| by a long shot | | | |
| by a long way | | | |
| by and large | | | |
| by an eyelash | | | |
| by any means | | | |
| by any stretch of the imagination | | | |
| by far | | | |
| by guess or by gosh | | | |
| by halves | | | |
| by hand | | | |
| by hook or by crook | | | |
| by mistake | | | |
| by no means | | | |
| by no stretch | | | |
| by no stretch of imagination | | | |
| by no stretch of the imagination | | | |
| by one's lights | | | |
| by one's own hand | | | |
| by right | | | |
| by the book | | | |
| by-the-book | | | |
| by the eye | | | |
| by the Grace of Allah | | | |
| by the Grace of God | | | |
| by the moment | | | |
| by the numbers | | | |
| by-the-numbers | | | |
| by the same token | | | |
| by the score | | | |
| by the skin of one's teeth | | | |
| by the way | | | |
| by trade | | | |
| by vice of | | | |
| by virtue of | | | |