noun
street clothes; outdoor clothes; clothes for going out
Refers to clothing worn outside the home, as opposed to indoor wear or loungewear. Often used in contrast with 部屋着 (indoor clothes).
部屋着から外出着に着替える。
I change from indoor clothes to outdoor clothes.
急な来客で、あわてて外出着を着た。
With an unexpected visitor, I hurriedly put on my street clothes.
普段着 is everyday casual wear, which can be worn both indoors and outdoors, whereas 外出着 specifically implies clothes for going out.
Compound of 外出 (going out) and 着 (clothing).