A nod usually signifying a greeting or the "what's up" as you may. The "sup" nod is usually used for "lax" brahs or other brahs that are too lazy to give daps to each other or don't feel like talking. Another use of this is to avoid the awkward daps and miss, or to avoid attention so that people don't see you associating with that person. Usually used during the winter months because everyone is a zombie in the morning at school. The nod is usually upwards.
Brah 1: Sup brah, I was chilling with my girl walking down the hall and Jacob walked down past me so I didn't want to leave him hanging so I gave him the "sup" nod.