Definition of "amaracus"

Then to the bower they came, / Naked they came to that smooth-swarded bower, / And at their feet the crocus brake like fire, / Violet, amaracus, and asphodel, / Lotos and lilies: and a wind arose, / And overhead the wandering ivy and vine, / This way and that, in many a wild festoon / Ran riot, garlanding the gnarled boughs / With bunch and berry and flower thro' and thro'.

1842, Tennyson, “Oenone”, in The Lady of Shallot and other poems