What it means

1. verb make a copy of (a computer file) especially for storage in another place as a security copy
   “You'd better back up these files!”
2. verb move backwards from a certain position
   “The bully had to back down”
3. verb establish as valid or genuine
   “Can you back up your claims?”
4. verb give moral or psychological support, aid, or courage to
   “She supported him during the illness”
5. verb become or cause to become obstructed
   “The leaves clog our drains in the Fall”