everyday clothes; ordinary wear
Rare, somewhat dated term for clothes one wears daily; modern Japanese more commonly uses 普段着 (ふだんぎ).
「平生着」 is an old-fashioned word meaning the same as 普段着 (everyday clothes).
Compound of 平生 (へいぜい, 'usual, ordinary') and 着 (ぎ, 'clothing'). The exact historical usage is uncertain, but it appears to be a less common variant of 普段着.