Gentian n. : Any one of a genus (Gentiana) of herbaceous plants with opposite leaves and a tubular four- or five-lobed corolla, usually blue, but sometimes white, yellow, or red. See Illust. of Capsule.

Example:
Is it okay to start using Gentian violet again, after having used it before?

Taxonomy
Gentian, species, Gentiana, unranked, flowered species, free encyclopedia, Gentiana verna, Autumn Gentian, poem, Gentian family, Closed bottle Gentian, Willow Gentian, Gentiana calycosa, Fringed Gentian, Great Yellow Gentian, Marsh Gentian, Spring Gentian, Species classification.

Defination from the web:
Gentian is also used as a flavouring, for example in bitters, and the soft drink "Moxie" which contains "Gentian Root Extractives" ... All gentian species have terminal tubular flowers and most are pentamerous, i.e. with 5 corolla lobes (petals), and 5 sepals, but 4-7 in some species. ...