Down with somebody/something Definition 1 of 3Pro Tip 1/3Casual Agreement Used among friends to show casual support, often less formal than outright agreement. Sure, I'm down with hanging out tonight. Pro Tip 2/3Slang Nuance It's a slang phrase; avoid in formal writing or speeches but common in everyday conversation. You're starting a book club? I'm down with that! Pro Tip 3/3Enthusiastic Participation Conveys enthusiasm to participate; more active than passive agreement. A road trip this weekend? I'm totally down with it!