a person who does not seem very friendly and does not show their emotions.

He isn't very demonstrative, but his mother was a cold fish so he probably gets it from her.

• the beau monde
• the beauty of
• the beauty of something
• the beginning of the end
• the best of both worlds
• the best of the best
• the best of the lot
• the best thing since sliced bread
• the better part of
• the better part of something
• the Bible Belt
• the big daddy
• the bigger they are, the harder they fall.
• the big picture
• the big smoke
• the big time
• the bird has flown.
• the birds and the bees
• the biter bit
• the biter is bit
• the bitter fruits
• the black sheep
• the black sheep of the family
• the blind leading the blind
• the blue blazes