back up (v.)give moral or psychological support, aid, or courage to;
back up (v.)move backwards from a certain position;
back up (v.)establish as valid or genuine;
Can you back up your claims?
back up (v.)make a copy of (a computer file) especially for storage in another place as a security copy;
You'd better back up these files!
back up (v.)become or cause to become obstructed;
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