バック

1. noun back; rear
2. background; backdrop
3. backing; support; backer; supporter
4. noun, takes する, intransitive going backwards; reversing; backing up
5. noun, abbreviation reverse (gear)
6. noun, takes する, transitive refunding; returning (e.g. profits)
7. noun, sports back (player)
8. abbreviation backstroke (swimming)
9. abbreviation, sports backhand
10. slang doggy style (sexual position)