1. move backward; move in reverse. (no object)
2. drive a vehicle backwards (in reverse) (separable)
3. confirm a story, facts, or information. (separable)
4. make a copy of computer data (separable)
1. cofnąć się
3. potwierdzić, poprzeć
4. zrobić kopię bezpieczeństwa
1. "The people waiting in line are too close to the door. We won't be able to open it unless they back up."
2. "You're too close! Back your car up so I can open the garage door."
3. "If you don't believe me, talk to Dave. He'll back me up."
4. "When my computer crashed, I lost many of my files. Fortunately I had them backed up."