adjective

1. having no fixed course or purpose; irregular; random; wandering
2. deviating from the normal, conventional, or customary course; eccentric; queer
3. Geol. designating a boulder or rock formation transported some distance from its original source, as by a glacier

Etymology: ME erratik < OFr erratique < L erraticus, wandering < pp. of errare: see err

noun