vexillum

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A usually square banner hung from a crossbar on a staff, used as a military standard in ancient Rome.
• noun Zoology The weblike part of a feather; the vane.

from The Century Dictionary.

• noun In Roman antiquity: Strictly, the standard of a maniple; hence, any military standard, whatever its character, except the eagle of the legion.
• noun The troops collected under a vexillum; a company; a troop; any body of soldiers serving under an ensign separate from that of the legion; hence, under the empire, the body of veteran soldiers connected with a legion who, having served sixteen years in the legion, were detached under a vexillum of their own, with special privileges, for their remaining four years of service. These vexilla averaged from 500 to 600 in strength.
• noun Eccles.: A processional banner; also, a processional cross.
• noun A kind of flag or pennon attached by a cord to the upper part of a bishop's pastoral Staff.
• noun In heraldry, same as banderole, .
• noun In botany, the standard, or large posterior petal, of a papilionaceous flower. It is external, and wrapped around the others in the bud. Also vexil. See cut under papilionaceous.
• noun In ornithology, a pogonium. web, or vane of a feather; also, both webs together with the rachis upon which they are borne. Also called standard.

from the GNU version of the Collaborative International Dictionary of English.

• noun A flag or standard.
• noun A company of troops serving under one standard.
• noun A banner.
• noun The sign of the cross.
• noun (Bot.) The upper petal of a papilionaceous flower; the standard.
• noun (Zoöl.) The rhachis and web of a feather taken together; the vane.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A flag, banner, or standard.
• noun A company of troops serving under one standard.
• noun The sign of the cross.
• noun botany The upper petal of a papilionaceous flower.
• noun zoology The rhachis and web of a feather taken together; the vane.