autological
Possessing the property it describes.
The word polysyllabic is autological, but the word monosyllabic is not.
Where it comes from
From German autologisch, from Ancient Greek αὐτός (autós, “self”) + λόγος (lógos, “word”), by surface analysis, autology + -ical.
Adapted from the Wiktionary entry autological (CC BY-SA 4.0).