Slang for scabies. They're small mites that burrow into the skin and lay eggs. They cause intense itching and are passed through skin to skin contact or exposure to them in bedding or clothing. While not always passed via sexual intercourse they frequently are in teenagers and young adults.
Bobby: Whoa man check out Dylan he's scratching like his whole body is on fire!

Jay: Yeah man he's got that STM...

Bobby: What the fuck is an STM?!

Jay: It's scabies. They're a STM (sexually transmitted mite). He supposedly got it from that broad he was humpin'.

Bobby: Wait. Isn't that what you just had?

Jay: I don't want to talk about it.
by Biggest Rockstar sans Band January 27, 2009
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Noun: Down Syndrome received by having sexual intercourse with a retard who appears to be suffering from Down Syndrome whether or not he actually does suffer from Down Syndrome.

Usually it's just a faggot who thinks he's hot shit.
"Lindsay" Lohan caught Sexually Transmitted Down Syndrome (STDS) from having sex with that one douche Matthew.
by Landon Smithismith June 11, 2008
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The name speaks for itself. Someone who gets around and not in a glorious way. The kind of person you're reluctant to shake hands with if you're not wearing both rubber gloves and a space suit.
Don't go out with that girl. Sure she's easy but she's a walking canister of every disease ever transmitted sexually.
by Sam is a Dick May 8, 2007
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A condition in which a previously lazy person becomes a sweat after getting with someone keen
He contracted Sexually Transmitted Keenness and now he's accessing all the top grades
by __AON__ November 7, 2017
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