verb (v)

• give moral or psychological support, aid, or courage to(verb.social)

  Synonym:
  support
  

  source: wordnet30
• move backwards from a certain position(verb.motion)

  Synonym:
  back down, back off
  

  source: wordnet30
• establish as valid or genuine(verb.change)

  Example:
  Can you back up your claims?.
  

  Synonym:
  back
  

  source: wordnet30
• make a copy of (a computer file) especially for storage in another place as a security copy(verb.creation)

  Example:
  You'd better back up these files!.
  

  source: wordnet30
• become or cause to become obstructed(verb.contact)

  Synonym:
  choke, choke off, clog, clog up, congest, foul
  Antonym:
  unclog
  

  source: wordnet30