American armhole
A wasei-eigo term used in fashion and sewing to refer to a set-in sleeve with a deep, rounded armhole, typical of American-style casual wear like T-shirts.
wasei-eigo (Japanese-coined English), from American sleeve
This T-shirt has American armholes, so it's easy to move in.
The pattern explains how to sew an American armhole.
Variant with interpunct; less common but seen in some contexts.
Wasei-eigo from English 'American' + 'sleeve', referring to a sleeve style associated with American casual clothing.