Wearing thick clothes; dressing warmly (to protect against cold).
冬は厚着をして出かけたほうがいい。
It's better to dress warmly when going out in winter.
まだ寒いからあまり薄着しないで、厚着してね。
It's still cold, so don't wear light clothes; dress warmly.
彼は風邪をひかないように厚着をしていた。
He was dressed warmly so as not to catch a cold.