A RachelBRB (be right back) is when one person says BRB on instant messager with the intention of signing off and returning at a much later time. It should be substituted with a BBL (be back later).
Rachel: BRB!
Bob: Okay.
Rachel: Signing off 5:30pm.
Rachel: Signing on 10:00pm.
Rachel: I'm back
Bob: Away Message Response: Went to bed.
Hence, A Rachel BRB, and not a typical BRB.
Excess drinking leads to disgracing yourself on the tube, going to ex boyfriends house and then having to go to work the next day in his flatmates clothes and shoes with soiled clothes in a plastic bag. Work mates then class this as 'doing a rachel'