Buckle up

to fasten a seatbelt in a car or on a plane

bugger off INFORMAL

If you tell someone to bugger off, you're telling them to go away in a very impolite and aggressive way.

build on (1)

to add to what you've already succeeded in doing

build on (2)

to add a new section to a house or a building

build up (1)

to work at something and make it get stronger or bigger

build up (2)

to gradually increase

Bump into

to meet somebody by chance

Burn down

If something like a building or a forest burns down, it's completely destroyed in a fire.

burn out (1)

If a fire burns out, it slowly dies down until it stops burning altogether.

burn out (2)

to work too hard and suffer from physical and mental exhaustion

Butt in

to start talking when somebody else is already talking

Butt out INFORMAL

If you want to tell someone quite forcefully to mind their own business, you can tell them to butt out.

Butter up

to say nice things to someone before asking them to do something for you or to give you something