If you want to "rizz" someone, you want to flirt with or charm them. "Rizz" was popularized by live streamer and YouTuber Kai Cenat, who used the term around 2021, according to Dictionary.com.

GRATHWOHL: Rizz - it's clearly a youth culture word that's come out of their social media activity, and so much of social media has amplified the voice of youth culture in the mainstream.