When you express something indirectly, you say it implicitly. Your sister might implicitly suggest that you're the one who ate the last cookie by glaring at you then looking at the empty plate.
When you communicate something implicitly, you don't say it directly. Instead, you might drop hints or let your actions express it, like when a teacher doesn't stop a kid from bullying another, which implicitly says it's okay to bully. Implicitly can also be a synonym for absolutely — you trust your best friend implicitly: completely, without any reservations.