Bump thrust is an option available on the IAE V2500 series engines fitted to the A320 series which is selected by a little button on each thrust lever after engine start and adds something like 5% to TOGA thrust for getting out of places which normal TOGA will not allow. Trouble is that it plays havoc with engine life.
Doubtless those with more knowledge than me will fill you in on the technicalities.
Cheers,
mcdhu