eccentricityEnglishOxford New American Dictionaryeccentricity /ˌeksenˈtrisədē, ˌɛksɛnˈtrɪsədi / ▸ noun (plural eccentricities) 1 the quality of being eccentric: the eccentricity of his views. ▪ (usually eccentricities) an eccentric act, habit, or thing: her eccentricities were amusing rather than irritating. 2 technical deviation of a curve or orbit from circularity. ▪ a measure of the extent of a deviation of a curve or orbit: Halley's Comet has an eccentricity of about 0.9675.