I first heard the term used in a new context while watching the movie ATL. During an argument at a house party, Rashad's girlfriend, New-New, calls his ex-girlfriend, Tonya, "thirsty". Without going to urbandictionary.com, I quickly figured out from the situation that being thirsty means trying too hard to gain someone's attention and, ultimately, their affection. If you've seen ATL, you know that this wasn't Tonya's first time trying to win back Rashad, and it wasn't her first time getting curved by Rashad, either. The scene above simply shows how desperate (the non-slang version of thirsty) she was.
Thirstiness has existed long before we started calling it that. We see it in our everyday lives, in social media, movies, everywhere. Men and women alike shamelessly vying for attention, be it from that special someone who doesn't consider them equally special, or just every member of the opposite sex in general. However, just like the words I mentioned before and more, I think people are reaching a bit with their application of the word. Really reaching. I mean like, Go-Go Gadget Arm reaching.
I can't speak to women's experiences with men misinterpreting their actions as thirst (I'm very sure it happens; ladies, feel free to chime in and comment with your point of view), but I have definitely seen numerous cases where women misinterpret certain behaviors from men as thirst. I could understand if a guy is making unwarranted advances on a lady while she's working out, going through a woman's Facebook or Instagram account and liking 30-teen pictures in the span of 5 minutes, leaving comments on pics she posted 75 months ago, or sending numerous texts without responses (in which case I can't help but give the side-eye to the woman who gave him her digits in the first place, but that's neither here nor there). That kind of behavior is really obvious and over-the-top, and is definitely thirsty. However, let's not confuse these desperate actions with genuine compliments and legitimate persistence, which old-fashioned people would consider "chivalry" and "courting". These are also the kind of actions that most self-respecting women would want to see from a man to convince them that said man was interested. Sad thing is, even these things are being diagnosed as "thirst" nowadays. Some women will even take a simple, stand-alone compliment as thirst. I've seen guys post (what seems to me as) regular, respectful compliments on women's social media pictures, only to have the woman herself, one of her female "friends" online --heck, even other guys-- accuse it of being "thirsty". Honestly, in the majority of cases I've seen, it's usually not a case of the guys or girls being thirsty, but the accuser needing a reality check. In my humble opinion, any person who misinterprets thirst in such a way is either a jealous guy, or an insecure woman in need of validation or an ego-boost.
Speaking of seeking affirmation, that leads me to another phenomenon that has spread like wildfire in the world of social media: thirst traps. "What the heck is a thirst trap?" you might ask. (Warning: the previous link has scantily clad pictures that I'd rather not actually post, but there's no other way to describe what I'm talking about. Click at your own risk.) A thirst trap is when someone, usually a woman (not saying men don't set thirst traps, I've just never seen one, nor do I care to), posts a picture that is obviously designed to attract attention from the opposite sex, then when the floodgates inevitably open, resulting in craptons of "thirsty" likes and comments, she proceeds to dismiss all her likers and commenters as "thirsty." When I say "obviously designed to attract attention from the opposite sex", I'm referring to pictures where women have their "girls" hanging out on display, or are taking a bathroom mirror selfie while sitting on the sink in an attempt to amplify their "assets". Some of these pictures have captions that appear to be innocently calling attention to something else, like "I've been working on my abs, look at my progression!!!" when the girl is in a two piece, and it's obvious that her other parts are more prominent than her abs, or "New pillows on my bed!!!", but the "pillows" on display have a thong between them, and the real pillows are playing the background. Any person with half an ounce of sense can see that these setters of thirst traps know exactly what they're doing: seeking attention for themselves while disguising it in a way that makes it appear that others are thirsting for their attention. I dare to say that anyone who sets a "thirst trap" is just as thirsty, if not more thirsty, than the people getting caught in them.
So yeah... the thirst is indeed real. Just not as real as some would have us believe. Yes, there are thirsty people out there who legitimately need to be called out on it. Likewise, there are plenty of people accusing others of thirst who really just need to get over themselves.