Definition for essential oil: a volatile oil having the odor or flavor of the plan from which it comes; used in perfume and flavorings. Listed synonyms: balsam, essense, extract, volatile oil, patchouli, perfume. (From: Synonyms for ESSENTIAL OIL - Thesaurus.net)
Below is a sample ebook from the library's catalog.
(Image from: Synonyms for NUTRITION - Thesaurus.net)