When a group or individual slowly and casually approaches another group or individual from a distance, gaining the attention and curiosity of those being approached. When the approacher(s) get close, they proceed to suddenly and violently beat the shit out of fucking everyone, catching them completely off guard.
Typical behavior while performing the slow rush involves putting one's hood up, covering one's mouth with one hand and letting the other arm hang and move from side to side while walking, leaning slightly forward, and having one's head move around erratically due to scanning for cops in the area. The behavior is noticeably suspicious, but does not alert the victims of the oncoming vicious assault. It serves only to gain the curiosity of the victims so they are drawn in and wonder what in the fuck you are doing.
Opening attacks just as the victims are approached tend to be the sucker punch to the face, the sucker slap to the face, putting the victim in the clinch and then performing repeated running knees to the the gut and groin, judo throwing them to the ground, or explosively tackling them, mounting them, and punching their face.
Joe: Yo look at those douchebag kids over there
Jesse: Yeah, let's go slow rush those mother fuckers
Joe + Jesse: *put hoods up*
Joe: Let's do this