This is the 8764th most frequent Korean word.
갈아입은
"Changed clothes"
In this case, '갈아입은' is part of the description of a sequence of actions, showing the completed action of changing clothes before leaving.
그는 갈아입은 후에 바로 집을 나갔어요.
He left the house immediately after changing clothes.
Here, '갈아입은' describes the shirt someone has changed into, providing context for the compliment.
갈아입은 셔츠가 정말 잘 어울려요.
The shirt you changed into looks really good on you.
In this sentence, '갈아입은' represents the action of having changed clothes, indicating a completed action connected to the feeling afterwards.