Back the wrong horse
Back to basics
Back to square one
Back to the drawing board
Back to the salt mines
Back up (someone or something)
Back-to-back
Bad blood (between people)
Bad egg
Bad hair day
Bad-mouth (someone or something)
Bad/rotten apple
Badger (someone)
Bag of tricks
Bail (someone or something) out
Bail (someone) out
Bail a company out
Bail out (of something)
Balance the books/accounts
Ball is in (someone's) court
Ball of fire
Ball park figure/estimate
Ballpark estimate/figure
Balls of one's feet
Bang for the buck
Bang/beat one's head against the wall
Bank on (someone or something)
Banker's hours
Bankroll someone
Baptism of fire
Bare bones (of something)
Bargain for (something)
Bargain on (something)
Barge in on (someone or something)
Bark is worse than one's bite
Bark up the wrong tree
Base one's opinion on (something)
Bat a thousand
Bat out of hell
Bats in the belfry
Batten down the hatches
Bawl out (someone)
Be a new one on (someone)
Be all ears
Be all things to all people
Be at one's wit's end
Be cricket
Be curtains for (someone or something)
Be dealt a bad hand/deal someone a bad hand
Be game
Be hand in hand
Be into (something)
Be laid up
Be of the persuasion that (something) is so
Be off
Be off on the wrong foot
Be off to a bad start
Be that as it may
Be the case
Be the death of (someone)
Be to blame
Be/have something going for (one)
Bean counter
Bear (someone or something) in mind
Bear (something) out
Bear fruit
Bear in mind
Bear one's cross
Bear the brunt of (something)
Bear with (someone or something)
Bear witness (to something)
Bear/hold a grudge (against someone)
Beat (someone) to the punch/draw
Beat (something) into (someone's) head
Beat a hasty retreat
Beat a path to (someone's) door
Beat around the bush
Beat one's brains out
Beat one's head against the wall
Beat the clock
Beat the gun
Beat the living daylights out of (someone)
Beat the rap
Beat the tar out of (someone)
Beat up (someone)
Becoming on/to (someone)
Beef up (something)
Before long
Beg the question
Beg to differ with (someone)
Begin to see the light
Behind (someone's) back
Behind closed doors
Behind in/on (something)
Behind one's back
Behind schedule
Behind the eight ball
Behind the scenes
Behind the times
Belabor the point
Believe one's ears
Believe one's eyes
Below average
Below par
Belt (something) out
Bend (someone's) ear
Bend over backwards (to do something)
Bent on doing (something)
Beside oneself (with something)
Beside the point
Best bib and tucker
Best-laid plans of mice and men
Best/better part of (something)
Bet on the wrong horse
Bet one's boots
Bet one's bottom dollar
Better off
Between a rock and a hard place
Between the devil and the deep blue sea
Betwixt and between
Beyond a reasonable doubt
Beyond a shadow of a doubt
Beyond measure
Beyond one's depth
Beyond one's means
Beyond the pale
Beyond words
Bid adieu to (someone or something)
Bide one's time
Big cheese
Big cheese/gun/wheel
Big enchilada
Big fish in a small pond
Big frog/fish in a small pond
Big of (someone)
Big shot
Bigmouth
Bigwig
Binge and purge
Bird brain
Bird in hand is worth two in the bush
Bird in the hand is worth two in the bush
Birds and bees
Birds of a feather flock together
Birds-eye view
Birthday suit
Bite (someone's) head off
Bite off more than one can chew
Bite one's nails
Bite one's tongue
Bite the bullet
Bite the dust
Bite the hand that feeds (someone)
Bite the hand that feeds one
Bitten by (some kind of) bug
Bitter pill to swallow
Black and blue
Black and white
Black box
Black eye
Black market
Black out
Black sheep of the family
Black-tie event/affair
Blackball (someone)
Blacklist (someone)
Blackmail (someone)
Blackout
Blast off
Blaze a trail (in something)
Bleeding heart
Bleep (something) out
Blessing in disguise
Blind date
Blind leading the blind
Blood is thicker than water
Blood runs cold
Blood, sweat, and tears
Blow (someone or something) off
Blow (someone's) cover
Blow (someone's) mind
Blow (someone) away
Blow (something)
Blow (something) out of all proportion
Blow a fuse
Blow one's nose
Blow one's own horn
Blow one's stack/top
Blow one's top/stack
Blow over
Blow the lid off (something)
Blow the whistle on someone
Blow to smithereens
Blow up (at someone)
Blow up in (someone's) face
BLT
Blue blood
Blue in the face
Blue-ribbon
BO
Body blow
Bog down
Boggle one's mind
Boil down to (something)
Bona fide
Bone of contention
Bone up (on something)
Bonehead
Booked solid
Bookworm
Boot out
Bore (someone) stiff/to death
Bored out of one's mind/skull
Born out of wedlock
Born with a silver spoon in one's mouth
Bosom friend
Boss (someone) around
Bottle (something) up
Bottom dollar
Bottom drops/falls out of (something)
Bottom line
Bottom out
Bottoms up!
Bounce a check
Bounce something (an idea) off someone
Bound and determined
Bound for somewhere
Bound hand and foot
Bound to (do something)
Bow and scrape
Bow out
Bowl (someone) over
Boys in the backroom
Brain (someone)
Brain drain
Brain teaser
Brainchild
Brainless
Brains behind (something)
Brainstorm something
Brainwash (someone)
Brand-new
Breach of promise
Breach of the peace
Bread and butter
Bread and water
Break (someone's) fall
Break (someone's) heart
Break (something) down
Break (something) to (someone)
Break a habit
Break a law
Break a leg!
Break a record
Break camp
Break down
Break down (something)
Break even
Break fresh/new ground
Break ground for (something)
Break in (someone or something)
Break into a cold sweat (about something)
Break into tears
Break loose (from someone or something)
Break off
Break one's back/neck (to do something)
Break one's word
Break out in (something)
Break out in a cold sweat
Break out of (something)
Break the back of (something)
Break the bank
Break the ice
Break the law
Break the news (to someone)
Break through
Break up (with someone)
Breakthrough
Breath of fresh air
Breathe down (someone's) neck
Breathe easy
Breathe easy/easier
Breathe one's last
Brew a plot
Bright and early
Bright-eyed and bushy-tailed
Brimming with (something)
Bring (someone or something) to its/their knees
Bring (someone) around
Bring (someone) into line
Bring (someone) to
Bring (someone) to heel
Bring (someone) to terms
Bring (something) home to (someone)
Bring (something) into question
Bring (something) off