A combination of dead skin cells, seminal fluid and excess urine.

It's a natural process that starts during the mid-teen years. The dead skin cells are from the connective tissue that held the foreskin to the glans during childhood.

As soon as you hit your teens, this tissue breaks down which then allows you to retract your foreskin.

Smegma can be washed out with plain water. Make sure you carefully retract your foreskin. Smegma usually builds up behind the inner end of the glans (just behind the bell-shaped tissue known as the corona). Soap isn't advised for use to keep skin irritation to a minimum, especially around such a sensitive area.

In case of smegma, circumcision isn't necessary. Smegma isn't a disease or a form of fungus. Just follow the above steps.
"You have a case of smegma. Just use plain water to wash it out."
by DylRicho March 16, 2013
Foul cheese like buildup that comes from not washing or properly maintaining equipment. It comes from NOT WASHING YOUR DISGUSTING TWAT/COCK! See egg salad.
You have smegma leaking from your pants you dirty fuckwad!
by Not so super DJ Gennady March 7, 2003
A term which can be referred to as the cheesy substance caused from sweating of the gland. More common with people who have a foreskin or skanky dirty bastards that don't wash.
"I went to take a piss the other day and because I hadn't washed in a while my dick smelt cheesy."
by Doc December 12, 2002
Smega is a cheesy-like substance which can build up in the genitila area. Usually occuring in the male genetilia, this substance has a cottage-cheese like texture and creamy in colour, it build up around the edges of the head of the male's penis. This mostly happens for men who have not been circumzized, considering the foreskin covering skin, thus germs/bacteria build up may lead to this fungus growth. It most likely has a fowl smell and people may not like knowing that you have smegma growth. Your partner will not appreciate either. To clean, take your tooth-brush and gently scrub the circumfrence of the head of your penis. Simply rinse the brush and you're set. To avoid re-occurences of smegma build up, you should consider cirzumsizion, or, if you are circumzized, soap your shaft on a regular basis to keep hygiene in tact.
Cory noticed a fowl, musty tinge protruding from his genetila. In shock, he analyzed the oozy-fungus growing on his mandhood, he determined it was the infamous, smegma. He pulled back his foreskin and witnessed a light-yellow-creamy-like substance growing like a fungus on a mushroom, but around the rim of his penis head. He quickly took his toot-brush and scrubbed it off. To prevent this, he frequently cleaned under his foreskin and washed his shaft.
by Jacekkk November 4, 2006