Noun
One of the feathers on an arrow that is placed at right angles to the nock on the bow, usually having a different color than the other feathers so that it is easily identified.
The tailfeather of a cock.
Alternative form of cock feather
Feather on an arrow.
Tailfeather of a cock.
Source: en.wiktionary.orgcock-feather
Commonly, the cock feather is of a different color. Source: Internet
Typical arrows with three vanes should be oriented such that a single vane, the "cock feather", is pointing away from the bow, to improve the clearance of the arrow as it passes the arrow rest. Source: Internet