Wagering is a synonym for betting or staking. In the context of a bonus's wagering requirements, it points to a minimum cumulative bet that has to be made before you are allowed to withdraw funds. A simple example would be a bonus worth 544 pesos with a 30x wagering requirement. Said bonus would have to be wagered until a wagering total of 16.320 pesos is reached. Only then would you be allowed to withdraw without being penalized.