A long, fancy coat that people wear over their other clothes to keep warm.
Surtouts are often seen as very fancy and old-fashioned.
Examples:
The man wore a fancy surtout over his suit.
She put on her warm surtout before going outside.
The lady's surtout was very beautiful and warm.
I want a surtout like the one in the movie!
In the olden days, people wore surtouts to look very fancy.
The king's surtout was the fanciest of all.