A poo roller is the name given to a small piece of excrement that has been left behind in ones undergarments.

To be classed as a 'poo roller' the piece of excrement should be at least the size of a raisin, anything smaller and it is mealy a stubborn poo stripe or a textured skid mark. It should also be no larger than a grape as this then falls in to the category of a normal poo and would probably weigh too much to remain in ones undergarment.
For Example: At school when you had a swimming lesson (for those fortunate enough too have that facility) you would all get changed together and leave your undergarments hanging over the peg in the changing rooms. It was then common practice for children to then inspect the undergarments of other children in the search of poo stripes or skid marks.
Whilst this sneaky inspection was being carried out, sometimes as the elastic on the undergarment was lowered for inspection a small piece of excrement would roll freely (sometimes high into the air depending on the undergarments elastic) and resulting in either hitting the inspector straight in the face or speeding along the ground towards other petrified onlookers.

So be warned and watch out for that 'poo roller'!
by H20's April 4, 2008
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