Dick In A Haystack

It's when you are the only dude in a room full of hot chicks.
You are more likely to get laid, when you have the only swinging dick around.

Dude, did you hear? Evan got laid by three different chicks last night at the same time. How the fuck does that happen? He was the only dude left after the party. Like a dick in a haystack...of vaginas.

Oklahoma Haystack

When you pee in a girls butthole then them shitting on your dick while it’s still inside them.

Me and my girl just did an Oklahoma Haystack

Haystacking

The act of strategically restricting your Tinder settings in hopes of finding one person of interest. This is especially helpful if you want to make your intention to hook up clear without a discussion. Incredibly useful in a small-town where you want to know who's DTF.

Did you try haystacking that girl you met at the bar on Tinder? With the right location and age settings, it definitely won't take you more than two days to swipe through and find her if she's on there!

Needle in a Haystack

Usually used when someone's trying to do the impossible.

It's also used when you're coding

Needle in a haystack coding example:
strpos("haystack", "needle");