to wear extra clothes
to dress formally
寒い朝に厚着を着込んだ。
I wore extra layers on the cold morning.
子供が外出前に服を何枚も着込んでいる。
The child is wearing many layers of clothing before going out.
冬山に登る際はウールを重ねて着込む必要がある。
Layer up with wool when climbing a winter mountain.