Meaning

adjective lacking stability or fixity or firmness

adjective highly or violently reactive

adjective affording no ease or reassurance

originEtymology tree Proto-Indo-European *h₂ent- Proto-Indo-European *-s Proto-Indo-European *h₂éntsder. Proto-Germanic *anda- Proto-West Germanic *anda- Old English and- Old English on- Middle English on- English un- English stable English unstable From un- (reversive prefix) + stable.

Etymology from Wiktionary, CC BY-SA 3.0