back and forth

back and forth - going from one side to another - a problem or physically

back down

to back down - to retract an argument or opinion

back off

to back off - retreat or move back from something

back out of

to back out of - not do something you had previously agreed to do

back to basics

back to basics - to to go back and look at the important aspects of something

back to square one

to start again at the beginning

back to the drawing board

start the process again

backbone

backbone - to have honesty, determination and integrity

backlash

a negative reaction to a recent event

backlog

a large amount of work that has built up over time