A babe in arms is a very young child, or a person who is very young to be holding a position.
Babe in the woods
A babe in the woods is a naive, defenceless, young person.
Baby boomer
A baby boomer is someone born during 1945-1965, a period when the population was growing fast.
Back burner
If an issue is on the back burner, it is being given low priority.
Back foot
(UK) If you are on your back foot, you are at a disadvantage and forced to be defensive of your position.
Back the wrong horse
If you back the wrong horse, you give your support to the losing side in something.
Back to square one
If you are back to square one, you have to start from the beginning again.
Backseat driver
A backseat driver is an annoying person who is fond of giving advice to the person performing a task or doing something, especially when the advice is either wrong or unwelcome.
Bad blood
If people feel hate because of things that happened in the past, there is bad blood between them.
Bad egg
A person who cannot be trusted is a bad egg. Good egg is the opposite.
Bad taste in your mouth
If something leaves you with a bad taste in your mouth, you feel there is something wrong or bad about it.
Bad workers always blame their tools
"A bad worker always blames their tools" - If somebody does a job badly or loses in a game and claims that they were let down by their equipment, you can use this to imply that this was not the case.
Baker's dozen
A Baker's dozen is 13 rather than 12.
Bald as a coot
A person who is completely bald is as bald as a coot.
Ball is in your court
If the ball is in your court, it is up to you to make the next decision or step.
Ballpark figure
A ballpark figure is a rough or approximate number (guesstimate) to give a general idea of something, like a rough estimate for a cost, etc.
Banana republic
Banana republic is a term used for small countries that are dependent on a single crop or resource and governed badly by a corrupt elite.
Baptism of fire
A baptism of fire was a soldier's first experience of shooting. Any unpleasant experience undergone, usually where it is also a learning experience, is a baptism of fire.
Bar fly
A bar fly is a person who spends a lot of time drinking in different bars and pubs.
Barefaced liar
A barefaced liar is one who displays no shame about lying even if they are exposed.
Bark is worse than their bite
Someone who's bark is worse than their bite may well get angry and shout, but doesn't take action.
Barking up the wrong tree
If you are barking up the wrong tree, it means that you have completely misunderstood something or are totally wrong.
Barrel of laughs
If someone's a barrel of laughs, they are always joking and you find them funny.
Basket case
If something is a basket case, it is so bad that it cannot be helped.
Bat an eyelid
If someone doesn't bat an eyelid, they don't react or show any emotion when surprised, shocked, etc.
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