Contracting or catching something(s) NASTY, stemming from gonorrhea, chlamydia, etc. but more generally just something nasty, germy, or something you don't want to get, touch, associate with.
"I don't fuck with that girl, I don't want none of her gonna-clitty-clatty"
*friend eating cheetos on white couch* "go wash your hands, before you get that gonna-clitty-clatty all over my shit!
"Whew, your breath smell like you've been eating some gonna-clitty-clatty"
an evenbetter term for "swag". clatty can mean cool, awesome, etc. it is also not used by Justin Beiber, therefor it is way better than "swag".
"dang, he's got clatty."
"i know right!?"
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"do you see ALL THIS?"
"yeah..you got clatty."
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"dude, what did you see in her anyway?"
"only her clatty.."