ambisignum

The ambisignum is the ± symbol commonly referred to as the plus-or-minus sign, or the plus-minus sign. The term is derived from the Latin prefix 'ambi-,' which means "both" or "on both sides," reflecting the dual nature of the symbol (plus and minus). The Latin word 'signum' means "sign" or "symbol" and directly ties 'ambisignum' to its function as a mathematical sign.

Note that it is tautological to refer to an 'ambisignum sign' or an 'ambisignum symbol' in the same way that it is tautological to refer to RAS syndrome (where RAS means 'redundant acronym syndrome')...

Albert could never remember the keystrokes required to insert an ambisignum into his social media posts discussing mathematics, so he always resorted to copying one from a web search and pasting it into his text.