back up phr v 1 [T back sb/sth ↔ up] to support what someone is doing or saying, or show that it is true 支持〔某人做的事或说的话〕; 证实〔某事〕: He had evidence on video to back up his claim. 他有录像证据来证实他的说法。 2 [I,T back sth ↔ up] to make a copy of information on a computer 〔在电脑上〕复制（资料） 3 [I,T back sth ↔ up] to make a car go backwards 倒（车）