Latin for "We are in Rhodes; jump".
What? Do you need a little more context? Oh, well...
It's the punchline of a fable by Aesop ("The braggart", I think it's called), where an athlete was boasting about an incredible jump he made in Rhodes once - and he had witnesses to prove it!
A bystander uses the phrase to shut him up: there is no need for witnesses when you can demonstrate your ability here and now.
(The phrase is better known because it was used, out of context, by Hegel in his Philosophy of Right).
This useful trivia was brought to you by the "Stun your Opponent with Latin Phrases" corporation.