This character is a Math Symbol and is commonly used, that is, in no specific script.
The glyph is not a composition. It has no designated width in East Asian texts. In bidirectional text it acts as Other Neutral. When changing direction it is not mirrored. The word that U+25FF forms with similar adjacent characters prevents a line break inside it.
The CLDR project calls this character “lower right triangle” for use in screen reading software. It assigns these additional labels, e.g. for search in emoji pickers: lower, right, triangle.
The Wikipedia has the following information about this codepoint:
Geometric Shapes is a Unicode block of 96 symbols at code point range U+25A0–25FF.
Representations
System
Representation (click value to copy)
Nº
9727
UTF-8
E2 97 BF
UTF-16
25 FF
UTF-32
00 00 25 FF
URL-Quoted
%E2%97%BF
HTML hex reference
◿
Wrong windows-1252 Mojibake
â—¿
Encoding: GB18030 (hex bytes)
81 37 A2 36
RFC 5137
\u'25FF'
Bash and Zsh inside echo -e
\u25FF
C and C++
\u25FF
C#
\u25FF
CSS
\0025FF
Excel
=UNICHAR(9727)
Go
\u25FF
JavaScript
\u25FF
Modern JavaScript since ES6
\u{25ff}
JSON
\u25FF
Java
\u25FF
Lua
\u{25FF}
Matlab
char(9727)
Perl
"\x{25FF}"
PHP
\u{25ff}
PostgreSQL
U&'\25FF'
PowerShell
`u{25FF}
Python
\u25FF
Ruby
\u{25ff}
Rust
\u{25ff}
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