To masturbate in an event where there are only males participating. During the masturbation, the person is caught by another group of males. The person then makes lies and says he was doing something else, such as packing a tin. This is usually done in a bathroom stall.
"Dude, why is everyone making fun of Steven?"-John "Dude, he was caught spengeling!"-Mark "Ew!"-John
Originated in the UK rave scene, it's Used to describe someone who's over done it a bit & is clearly under the influence of drugs. A Spenger may well making a bit of a fool of themselves. (The variation of Spenger - 'Spengo' has also been overheard)