(n.) illegible handwriting
Henscratch. Pot-hookery. Griffonage. English has plenty of jokey nicknames for bad handwriting. But there’s also this considerably more formal-sounding term: scoteinography.
For those of you who asked, no, this has nothing to do with the relatively incomprehensibleness of Scots English. (Perish the thought.) Nor is it any other kind of slight against Scotland. The root here is actually skotos, a Greek word for darkness or shadow, in the sense that bad or illegible lettering obscures its meaning. It was that that inspired this word when it first emerged in the language in the late 1700s.
That same root, incidentally, is the origin of a handful of similar obscurity-laden words, including scotography (an old term for an x-ray image), scotoma (a medical term for dizziness, loss of consciousness, or dimness of vision), and scotoscope (a microscope or telescope that illuminates its subject).