It is a combination of the words slut and egg. A sleg is a woman who decides it is a good idea to get knocked up as much as possible. She basically use her eggs to get on the Maury show and go through as many guys until she finds her child support check. They continue to do this until they have several children. A slegg usually has a very low iq and no other talents besides being able to bear children and maybe give a good blowjob.
Britney is such a slegg, shes had 7 babies with 5 different men and is married to Juan who works at the 7-11.
Slegg - underachieving member of society that usually lacks a decent appearance.
"I am tired of those damn Slegg's always getting my order wrong at Mcdonalds"
"That slegg is taking forever to make my meal"
"That crappy slegg janitor needs to replace the urinal pucks."