| babe in arms | | | |
| babe in the woods | | | |
| babe magnet | | | |
| babies in the eyes | | | |
| baby and bathwater | | | |
| baby elephant in the room | | | |
| babysitter test | | | |
| baby up | | | |
| back at you | | | |
| back-burner | | | |
| backburner | | | |
| back-cloth star | | | |
| back down | | | |
| backfire | | | |
| back forty | | | |
| back gammon player | | | |
| backhanded compliment | | | |
| back in the day | | | |
| back in the game | | | |
| back in the groove | | | |
| back into | | | |
| back off | | | |
| back office | | | |
| back of one's hand | | | |
| back-of-the-envelope | | | |
| back-patty | | | |
| backpedal | | | |
| back-pocket | | | |
| back-to-back-to-back | | | |
| back to square one | | | |
| back to the drawing board | | | |
| back to the wall | | | |
| back up | | | |
| back up the truck | | | |
| backwards and forwards | | | |
| backwater | | | |
| bacon-faced | | | |
| bacon-fed | | | |
| bad actor | | | |
| bad apple | | | |
| bad books | | | |
| bad business | | | |
| bad company | | | |
| bad egg | | | |
| badge bunny | | | |
| badge of honor | | | |
| bad hair day | | | |
| bad iron | | | |
| bad joke | | | |
| bad looker | | | |
| bad news | | | |
| bad news bears | | | |
| bad old days | | | |
| bad penny | | | |
| bad taste in one's mouth | | | |
| bad trot | | | |
| bad word | | | |
| bag of bones | | | |
| bag of tricks | | | |
| bail out | | | |
| baker's dozen | | | |
| baker's half dozen | | | |
| bake up | | | |
| baking hot | | | |
| balance out | | | |
| balance the books | | | |
| bale up | | | |
| ball-breaker | | | |
| ball hog | | | |
| ballistic podiatry | | | |
| ball of fire | | | |
| ball of malt | | | |
| balloon goes up | | | |
| balloon knot | | | |
| ballpark estimate | | | |
| ballpark figure | | | |
| balls of steel | | | |
| balls-out | | | |
| balls to the wall | | | |
| balum rancum | | | |
| bamboo ceiling | | | |
| banana nose | | | |
| banana republic | | | |
| Banbury story of a cock and a bull | | | |
| band-aid | | | |
| band-aid solution | | | |
| band together | | | |
| bandwagon fan | | | |
| bandwagon jumper | | | |
| bane of someone's existence | | | |
| bang a uey | | | |
| bang away | | | |
| bang down the door | | | |
| banger | | | |
| bang for the buck | | | |
| bang one's head against a brick wall | | | |
| bang out | | | |
| bang some heads together | | | |
| bang straw | | | |
| bang to rights | | | |