babe in the woods, a - someone who has not had much experience of life and trusts other people too easily
baby boomer, a - someone who was born between 1945 and 1965, a period in which a lot of babies were born
back and forth - from one place to another and back to thefirst place
backroom boy, a - someone who does a lot of work in the type of job where they are not often seen by the publicbackseat, take a - if an activity takes a back seat, you spend less time doing that than other things
backseat driver, a - a passenger in a car who continuously tells the driver how they should drive
bad egg, a - someone who behaves in a bad or dishonest way
bad hair day, a - to not feel attractive or happy all day because you cannot make your hair look nice /not work as it should ( for machines )
bad name, give sth/sb a - to cause people to lose respect for something or someone
bad way, be in a - to be ill, unhappy, or in a bad state
bag lady, a - a woman who has no home and carries everything she owns around with her in plastic bags
bag of bones, a - person or animal that is extremely thin
baker's dozen, a - thirteen
ball and chain, a - something which limits your freedom
ball-breaker, a - a woman who does not like men and is unpleasant towards them
ball, have a ball - to enjoy yourself very much
ball, a whole new ball game, a totally different ball game - a completely different situation, often one which is difficult or which you know very little about
ballpark estimate/figure, a - a number which is only approximate, but which should be near to the correct number
balls-up, a - a situation in which everything goes wrong
banana republic, a - a small, poor country with a weak or dishonest government
baloney - nonsense 
bark up the wrong tree, to - to make the wrong choice andwaste one’s efforts
band-Aid, a - a temporary solution to a problem, or something that seems to be a solution but has no real effect
bang, not with a bang but with a whimper - if something ends not with a bang but with a whimper, it ends in a disappointing way
baptism by/of fire, a - a very difficult first experience of something
bargaining chip, a - something that you can use to make someone do what you want
barrel, not be a barrel of laughs - to not be enjoyable
barrel, have sb over a barrel - to put someone in a very difficult situation in which they have no choice about what to do
bash, have a - to try to do something, or to try an activity that you have not tried before
beat around the bush, to - to waste time by not giving a direct answer bed of roses, a - a comfortable, easy situation
before long - eventually, after some time 
big mouth, a - a person who talks too much and does not keep secrets
big time, the - a high level of successbitter pill to swallow, a - something difficult and unpleasantto experience
black market, the - the market not controlled by the government, where things are sold in private and often against the law
blood is thicker than water - relatives are the most important people
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bookworm, a - someone who reads a lot
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break the ice, to - to begin a conversation with a stranger
breeze, a - something easy for a person to do
bring down the house, to - to make an audience clap and laugh enthusiastically
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bury the hatchet, to - to agree to no longer be enemies
bushed - very tired, exhausted
by and large - mostly, most often
by heart - by memory
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