When you think that something looks like a penis, when it is quite obvious it's not...
When you draw a penis (or any sexual picture), and do a really detailed drawing around it to make it look like something else
People making gestures in Maths Textbooks =S
anything that is long and rounded at one end
anything that as two circles before it
the video "is it a penis" on youtube (Y)
When Darcy sees something in a mathsbook and says "that could SO be a penis..."