Sticky, foul-smelling white secretion around the base of a penis head made of pre-cum, urine, and penile lubricant. Usually forms due to infrequent or poor hygiene, typically on uncircumcised penises. Simply showering every 1-2 days will prevent buildup, or you can use the ol’ toilet paper method (you know what I mean) in a pinch.
When I see schmegma, I know I should’ve showered a long time ago.