Entry 1 sense Webster, 1913 Oleaginous /ōlˌ-ē-ăj'-ən-əs/ · O·le·ag·i·nous · IPA /ˌoʊ.liˈæd͡ʒ.ɪ.nəs/ 01 a. Having the nature or qualities of oil; oily; unctuous. 1. Having the nature or qualities of oil; oily; unctuous.