What 骀 means
Read the compound: tái is the horse branch; dài is 骀荡.
Shuowen Jiezi gives the earliest explanation I could verify: a horse whose bit has come loose. That failure leads to ‘inferior horse’, then to a literary metaphor for low ability, as in 驽骀.
The other branch, dài, covers breadth, release, calm manner, and spring scenery in 骀荡. Historical dictionaries also record 駘 in names and place names, and as a written form of 跆, ‘trample’.
Literary and dictionary-like; the surrounding word does the work.
Do not read 骀荡 as tái ‘inferior horse’.
What it means when someone sends it to you
3 readingsQuestions people ask
1Why does 骀 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 骀
骀\9A80Codes and encoding1 code points
A visible symbol can contain several code points. JS .length counts UTF-16 units; UTF-8 counts bytes.