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

Bring (something) on

Bring (something) to (someone's) attention

Bring (something) to a head

Bring about (something)

Bring down the house

Bring home the bacon

Bring home the importance of (something) to (someone)

Bring some new facts to light

Bring to mind

Bring up

Bring up (something)

Bring up the rear

Broad in the beam

Brown bag it

Brush up on (something)

Brush with the law

BS

BSc

Buck for (something)

Buckle down to (do something)

Budget crunch/squeeze

Bug (someone)

Bug-eyed

Build (something) to order

Build a case (against someone)

Build a fire under (someone)

Build castles in the air/in Spain

Build up (someone or something)

Build up to (something)

Bull in a china shop

Bump into (someone)

Bump off (someone)

Bundle of nerves

Burden of proof

Burn (oneself) out

Burn (someone) in effigy

Burn (something) to a crisp

Burn a hole in one's pocket

Burn down

Burn one's bridges behind one