ec·cen·tric / ikˈsentrik/ • adj. 1. (of a person or behavior) unconventional and slightly strange: my favorite aunt is very eccentric.2. technical (of a thing) not placed centrally or not having its axis or other part placed centrally. ∎  (of a circle) not centered on the same point as another. ∎  (of an orbit) not circular.• n. 1. a person of unconventional and slightly strange views or behavior: he enjoys a colorful reputation as an engaging eccentric.2. a disc or wheel mounted eccentrically on a revolving shaft in order to transform rotation into backward-and-forward motion, e.g., a cam in an internal combustion engine.DERIVATIVES: ec·cen·tri·cal·ly adv.

eccentric not concentric XVI (as sb. XV); not central or referable to a centre; irregular, odd XVII; sb. (person) XIX, after F. — late L. eccentricus, f. Gr. ékkentros, f. ek out, EX-2 + kéntron CENTRE; cf. (O)F. excentrique.
Hence eccentricity XVI.