ride along cheater

a person, namely a good friend of the person being cheated on, that accompanies the cheater in their debauchery with other woman and participates in activities and behavior that they know the friend/person being cheated on would disapprove of or would hurt their feelings.

meghan is really sick of Russ. his ride along cheater ass better not show his face here anymore.

ron, "wheres russ?"
meghan, "hes ride along cheating with clint today."