What does "across the pond" mean — and why is it funny?

informal, friendly

Meaning

On the other side of the Atlantic Ocean — used by British and American speakers to refer to each other's country.

Where it comes from

Recorded since at least the 1600s, it grew popular in transatlantic journalism and broadcasting in the 20th century as a light, chummy way to gesture at the UK–US relationship.

Why it is funny

The humor is pure understatement. The Atlantic is one of the largest bodies of water on Earth, and calling it a 'pond' shrinks it to something you could skip a stone across. Speakers know it is absurd, and that shared wink — we both know this is a ridiculous thing to call an ocean — is the joke.

Used in a sentence

"Our cousins across the pond spell it 'colour' with a u."