What ㎺ means
It stands for pW, a picowatt—not pW squared.
Here pW combines p, the SI prefix pico (one millionth of one millionth), with W, the SI symbol for watt. The square lets both Latin letters occupy one character cell in East Asian text, including vertical layouts. This compact unit form was carried through Korean and other East Asian character-set standards.
As a compatibility character, it is retained for older East Asian text. Compatibility normalization—a text conversion that replaces such forms with their underlying letters—changes ㎺ to pW and loses the square cell. Plain pW is clearer in ordinary technical writing.
Technical, compact notation for pW; the square frame reflects East Asian text layout.
Read it as pW; the square is a frame, not an exponent.
Don't confuse it with
4Questions people ask
1Why does ㎺ show as a box on some devices?
Because that device's fonts have no glyph for it. The character is still correct and still copies correctly — the box is a missing glyph, not a broken character.
How to type ㎺
㎺\33BACodes and encoding1 code points
A visible symbol can contain several code points. JS .length counts UTF-16 units; UTF-8 counts bytes.