Code point
U+229F
Glyph appearance depends on your fonts.
U+229F
SmU+229F SQUARED MINUS is a Unicode 16.0.0 character in the Math Symbol category. It belongs to the Mathematical Operators block.
Choose the representation you need, then copy its value.
U+229F
8863
⊟
⊟
⊟
E2 8A 9F
229F
0000229F
%E2%8A%9F
\u229F
\u229F
\u229F
\229F