The keyman is the person that at raves, parties and functions that have
alcohol, has a big ring in which everyone puts there car
keys. At the end of the function, to drive, you need to prove to the keyman that you are sober enough.
If you are told beforehand that a keyman with be present it is implied that
alcohol will be at the function.
When
people are telling other about a party when there are at
school they might say:
β Hey mate come to this function. The keyman is Alex.β
(Itβs implied that there will be
alcohol.)