The transatlantic accent is a deliberately learned speaking style that blends features of British and American English, rather than a natural regional accent. It was especially associated with old Hollywood, elite boarding schools, theater, and radio in the early to mid-20th century.

What it sounds like

People often describe it as polished, formal, and slightly “in-between” British and American. A common feature is dropping the “r” sound after vowels, so words like “car” or “winter” sound more like “cah” and “wintah”.

Why it existed

It was taught as a prestige accent, meant to sound refined and clear in public speaking and performance. Actors, broadcasters, and some upper-class Americans used it to project sophistication and neutrality.

Today

You mostly hear it in vintage films, old recordings, or when actors intentionally recreate it. It is not a native accent tied to one region; it is something people learn on purpose.

TL;DR: The transatlantic accent is a stylized, learned mix of British and American speech that was popular in early Hollywood and elite circles.