NSA
Short for no strings attached: sex without commitment, expectations or follow-up, the standard terms of a hookup.

NSA means no strings attached: sex without commitment, expectations or follow-up. In a profile or a message it sets the terms before anything happens: we meet, we have fun, nobody owes anybody a text the next day. It is the small print of the hookup, written in three letters.
NSA does not mean rude, and it does not mean unsafe. It means no relationship, no drama and no pretending this is a date. Good manners, consent and condoms or PrEP are not strings.
Where it comes from
"No strings attached" is an everyday English idiom for a deal with no hidden conditions, the kind printed on an offer or a free gift. Nobody can say exactly when it was first applied to sex, but it is easy to see why it stuck: in personal ads, where every word cost money, and later in short profile headlines, three letters did the job of a paragraph. On the gay apps it is now one of the most common acronyms of all.
How it is used today
On the apps NSA usually comes in a cluster:
- NSA fun: sex, and that is all.
- NSA, discreet: sex, and nobody hears about it.
- NSA, DL: sex with a man who lives as straight.
- NSA FWB: friends with benefits, a regular partner with no relationship on top.
The opposite end of the profile spectrum is "looking for dates", "LTR" (long-term relationship) or the dreaded "not here for hookups", usually written by a man who is, sometimes.
Close relatives
NSA is the spirit of much older gay institutions: the glory hole, the darkroom and cruising were all NSA before anyone used the letters. A JO buddy is often an NSA arrangement too, just with less undressing.
No strings doesn't mean no feelings. If one of you starts wanting more, say so: renegotiating an NSA deal is allowed.