Used to express someone's familiarity with popular culture or current events. I can't believe how much she knows about K-pop, she's totally with it.
Pro Tip 2/3
Not Serious
Often used in casual conversations rather than serious or formal discussions. You've got to be with it and join the banter on social media!
Pro Tip 3/3
Age-Neutral
Can refer to any age group staying aware of contemporary trends, not just young people. Even at 70, my uncle is so with it; he just started learning to code!