home wear; casual clothes worn at home
Refers to comfortable, everyday clothes worn inside the house, as opposed to going-out clothes.
帰宅したらすぐに家着に着替える。
I change into my home wear as soon as I get home.
休日は一日中家着で過ごす。
On my days off, I spend the whole day in my casual home clothes.
Compound of 家 (いえ, 'house, home') and 着 (ぎ, 'clothing, wear'). The reading いえぎ follows standard rendaku voicing of the second element.