A practise usualy undertaken by homosexuals whereby a group of men sit in a circle and wank each other off in quick succession. Usualy performed with some kind of lubricant such as a big slab of butter.
A: 'Cor blimey did you see that group of puffs having a monk's circle last night in that abandoned warehouse!'
B: 'Yea those dirty fuckers i saw they had a huge slab of butter with them as well! They were at it all night!'