repel

force back
push off

like charges repel

http://dictionary.kids.net.au/word/repel

http://www.bbc.co.uk/schools/ks2bitesize/science/physical_processes/magnets/read2.shtml

http://www.matsuk12.us/176120115181252763/blank/browse.asp?a=383&BMDRN=2000&BCOB=0&c=66468