A squircle is is a type of cross between a square and a circle, appearing to be a square with rounded-off corners. While it may be used informally, it is technically a superellipse approaching the shape of a square. This is very closely related to the rounded square, and visually they are nearly identical.
For those interested in the most technical definition, given the superellipse equation:
| X |n | Y |n
| --- | + | --- | = 1
| a | | b |
A squircle results when n = 4.