ok - the REAL definition of a rhombus is this:
n(primarily used in the UK): one or several nights of hard DRINKING and/or DRUGGING that leads to a loss of memory, a laundry list of offences, multiple contusions and/or lacerations to the face and body, and in rare cases - illegitimate children.
the Rhombus is not to be taken lightly - and is most often presented as an agreement between two parties in accordance with the plans for the evening(s)