An Aceifa is a season of raiding, where the Arabs of the Reconquista time would launch raids into Christian territory for slaves and plunder. However, the Christians also had their own ways of raiding their foes.
To soften up the defense of a city, the best possible strategy was to devastate the surrounding countryside: "to burn and harry the land" as historian harles Oman put it. Thus, before laying siege to a key city, the Christians launched raiding expeditions year after year that burnt crops and woodland, destroyed housing, and captured or killed as much of the outlying populace as possible. That gradually worked to weaken the city's defense, as the amount of food and troops available to support it declined.