RB

RB is an acronym for running back, which is an offensive position in football. The running back is primarily used to run the football in order to gain yards but is also responsible for blocking and catching the ball.

RBs typically line up next to or behind the QB. It is the second most important offensive position in the NFL and is used to keep defenses off-balance along with the passing game. RB often appears as RB1 or RB2 in fantasy football leagues to indicate the starting and second starting running backs on a team. Some examples of famous RBs include Jim Brown, Emmit Smith, Walter Payton, Adrian Peterson, Eric Dickerson, Gale Sayers, LaDainian Tomlinson, and Barry Sanders.

In emails, RB typically stands for "reply by." This acronym is almost always followed by a timeframe, such as EoD or "within seven days," within which you are meant to reply to the sender's email.

Some senders condense their RB timelines to +#, written as RB+1 (meaning reply within one day), RB+2 (reply within two days), and so on. RB may also be preceded by RR, an acronym which means "reply requested," or not followed by a timeframe, in which case RB stands for "reply back."