Hi, it means going across the Atlantic Ocean (i.e. from the USA to the UK or vice versa). We have a similar expression in Australia and New Zealand, where going from one country to another, we say to head across the ditch!

hi.Across the Atlantic Ocean, almost always referring to either the British Isles or the United States, depending on which side of the ocean the speaker is from. I think we're going to head across the pond to London for our vacation this summer. and also you look like elena from vampire diares :D