A person with drown symdrome (has an extra copy of chromosome 21) and anyone that is mentally retarted, or has a mental handicap. The Abbreviation is SW. The mass transportation of SWs in public schools is known as "The Stumbly Wumbly Parade". They are transported in yellow scool busses in Oakland, hense the phrase:
"I go hyphy, dumb, stupid, retarded, while ghost-riding the yellow bus"
Guy: Whats wrong with that guy over there, he seems retarded
Other Guy: He is, he's a stumbly wumbly