Dirty-somethings are people (usually guys) in their thirties who show up at social events of age groups far below theirs own, often high school or college parties and gatherings.

When you hear see or feel something that is wrong...gross..or just plain off, but also is kinda culturally awesome-

A respected dentist who lived in a wealthy suburb of Cincinnati and attended his local Methodist church every Sunday, the author of the book "Dirty Sanchez's Guide to Buck Nasty Sex," originally found sex surprisingly boring and unfulfilling. And it wasn't just the Ohio women. He often described his sex life as "cumming without really orgasming." Then one day he tried something different and experienced an intensely pleasurable orgasm--he had drawn the handlebars that would soon spread to faces around the globe. As he informed others of his amazing discovery, he became known to sex experts everywhere as "Dirty Sanchez." But this first patented move was only the beginning. "Dirty Sanchez" gave up dentistry and now dedicates himself full-time to discovering exciting new eye-popping, heart stopping sexual positions.

the act of being nasty or performing something nasty

dirty mind syndrome

n.
abr. DMS

Something usually experienced by those for whom sex is a large part of every-day life. Basically the act of taking any innocent thought or expression, and suggesting (or considering) something dirty arising from it.

When you bend your woman over a couch by and at some time during the love-making you pull out and let your friend take over without her knowledge. Then you run around and wave at her from the other side of the couch.

Bonus points if you yell to friend something like "Happy Birthday dude" or something appropriate.

when one is caught hanging out with a member of the opposite sex in which everyone knows the said one is interested when one is suppossed to or has actually said one is doing something else