back-up

名词 back-up:

1. an accumulation caused by clogging or a stoppage
   同义词：backup
2. someone who takes the place of another (as when things get dangerous or difficult)
   同义词：stand-in, substitute, relief, reliever, backup, backup man, fill-in
3. a subordinate musical part; provides background for more important parts
   同义词：accompaniment, musical accompaniment, backup, support
4. (computer science) a copy of a file or directory on a separate storage device
   同义词：backup, computer backup
5. the act of providing approval and support
   同义词：backing, backup, championship, patronage

动词 back-up:

1. give moral or psychological support, aid, or courage to
   同义词：support, back up
2. move backwards from a certain position
   同义词：back up, back off, back down
3. establish as valid or genuine
   同义词：back, back up
4. make a copy of (a computer file) especially for storage in another place as a security copy
   同义词：back up
5. become or cause to become obstructed
   同义词：clog, choke off, clog up, back up, congest, choke, foul

1. The police had military back-up.
   警方有军队作後盾。