You're most likely to encounter the adjective eccentric in a description of an unusual or quirky person — like a scatterbrained aunt who leaves her life savings to her cat. The meaning of ECCENTRIC is deviating from conventional or accepted usage or conduct especially in odd or whimsical ways. How to use eccentric in a sentence. Did you know? Synonym Discussion of Eccentric . ECCENTRIC definition: 1. strange or unusual, sometimes in a humorous way: 2. (of a circle) not having the same centre…. Learn more. Learn the meaning of eccentric as an adjective and a noun, with examples and usage. Eccentric can describe someone who acts strangely or unusually, or something that is not circular.