1A veteran of the oldest category in the Roman army, serving under a special standard.
2A Roman standard-bearer.
Of aestivation: having the petals arranged so that the large, posterior vexillum encloses the other, smaller petals of the corolla. Also more generally: relating to or pertaining to a vexillum; having a vexillum.
Late 16th century; earliest use found in Henry Savile (1549–1622), mathematician and classical scholar.