- back someone up
- back to normal
- back to the drawing board
- backbiting
- backchat
- backdate
- backfill
- backgammon
- background score
- backing
- backlash
- backlog
- backrest
- backseat
- backseat driver
- backspace
- backwards
- backyard
- bacteriology
- bad debt
- bad job
- badger
- badly
- badly cooked rice
- bae
- bael fruit
- bakelite
- baker
- bakery
- bald-headed person
- bald-pate
- bale out
- balkanise
- ball
- ball is in one's court
- balloon
- ballot box
- bamboo grove
- bamboozle
- banana fruit
- bandanna
- bandit
- banister
- bank balance
- banyan tree
- bar centric
- barb
- bardoltry
- bare
- barefaced
- bargain
- barista
- barracks
- barn owl
- barnet
- barometrical
- barometry
- barring
- barrister
- bartered goods
- bascule
- base
- base person
- baseless
- bash
- basil
- basis
- bask
- basket
- basorexia
- bastard
- batch
- bathing costume
- bathos
- baton round
- batta
- batten
- battered
- battery
- battle
- battle-front
- bauble
- baud
- bauxite
- bazaar
- bbs
- bc
- bca
- be a matter of opinion
- be all greek
- be at the zenith
- be awake to
- be carried away, get carried away
- be done with, have done with
- be good value for money
- be in a mess
- be in a mood
- be in good form
- be in somebodys power
- be in two minds