The Brief: As a verb, to "thizz" means to take a pill or hit of Ecstacy.

DEEP DIVE
As an action, to thizz means to take a pill of ecstasy, or XTC. However, there are several other variations of the term.
Come on everybody now’s the chance
F**k the Harlem Shake, this the Thizzle Dance!
– Mac Dre, Thizzle Dance (2002)
“Thizz’n” refers to the act of being high on ecstasy, similar to tripping. “Thizz Face” refers to someone’s facial expression while they’re high on ecstasy – it usually looks like the person smelled something bad.
Anna from Pen15 be having me WEAK look at her thizz face 🤣🤣🤣 pic.twitter.com/PQtyXX7sxQ
— tropicalShawtyy (@acidsoooup) March 10, 2019
Thizz originally derives from the “Thizzle Dance”, a song by San Francisco “Yay“-area rapper, Mac Dre.
Can you do the Thizzle dance?
— May 6 (@MrQuitGivinAFuk) March 13, 2019
The 2002 music video sparked the “Thizzle Dance Challenge”, similar to the TikTok Yee Haw Meme Challenge, where people would film themselves doing the Thizzle Dance and upload their videos on YouTube.