Lit - Originally meaning "illuminated", now commonly used to describe something exciting or excellent.
FOMO - Fear Of Missing Out, the anxiety that an exciting or interesting event may currently be happening elsewhere.
Salty - Being upset or bitter, especially when something doesn't go your way.
Ghosting - The practice of ending a personal relationship with someone by suddenly and without explanation withdrawing from all communication.
Flex - To show off, especially to show off one's wealth or status.