superellipse
A geometric shape defined by |x/a|^n + |y/b|^n = 1 with n > 2, intermediate between an ellipse and a rectangle. Technical term used in mathematics and design.
The superellipse is known for being used in design by Piet Hein.
From English 'superellipse', combining 'super-' and 'ellipse'. The Japanese term is a direct loan translation using スーパー and 楕円.