I always wondered what a ☐ was called.
Glyph availability
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If an application does not have access to a glyph, the character will usually be shown as the font's .notdef glyph ⟨⟩ which often appears as an empty box, ☐ (nicknamed "tofu" based on the shape), a box with an X in it, ☒, a diamond with a question mark, �, or a box with a question mark in it, ⍰.
The image is from here - What is the technical term for a replacement character if a font does not have a representation - Graphic Design Stack Exchange
Guy who's only eaten tofu before seeing his first square