Papiliona'ceous. adj. [from papilio, Latin.]

The flowers of some plants are called papilionaceous by botanists, which represent something of the figure of a butterfly, with its wings displayed: and here the petala, or flower leaves, are always of a diform figure: they are four in number, but joined together at the extremities; one of these is usually larger than the rest and is erected in the middle of the flower, and by some called vexillum: the plants, that have his flower, are of leguminous kind; as pease, vetches, &c. Quincy.