The Urban Diction defines "yee yee ass" as "something that looks extremely horrible." For context, it provides the following example: "If it wasn't for that yee yee ass haircut of yours, you'd already have a job right now."
The term, and the example of usage, are actually taken from a furiously profane Grand Theft Auto 5 cutscene in which Franklin gets absolutely roasted by Lamar. The segment was popularized all the way back in 2013—according to Know Your Meme, the clip was first uploaded to YouTube on September 17, 2013, the day GTA5 was released—but it's taken on a new life recently, as fans have begun creating and sharing some pretty fantastic variations of Franklin's verbal beatdown.
Some use the game's original dialog with different voices—Kermit the Frog, for instance—while others, like Yakuza's Kazuma Kiryu roasting Franklin with karaoke, take a more surreal approach. But a new one that appeared earlier today on the PlayStation Haven YouTube channel may top them all: It's a real-life reenactment of the scene featuring Shawn Fonteno and Slink Johnson, the voice actors who portrayed Franklin and Lamar in GTA5.
(The video is down here, rather than up top, because it is extraordinarily NSFW—and I say that as someone who is deeply immersed in videogaming culture on a professional basis. Consider yourself warned.)
The rapid-fire dialog still lands, but what really makes the reenactment work is the attention to detail: The clothing, the backdrop, the poses, and the lyrical denouement are all spot-on. There are a lot of creative takes on the segment floating around (here's Thomas the Train getting in on the action) but for my money, you can't beat the original, by the originals.
Speaking of which, here's the actual cutscene, taken from the PS4 version and uploaded in 2014: