'Cock feather' definitions:

Definition of 'Cock feather'

From: GCIDE

Cock \Cock\, n. [It. cocca notch of an arrow.]
1. The notch of an arrow or crossbow. [1913 Webster]
2. The hammer in the lock of a firearm. [1913 Webster]
At cock, At full cock, with the hammer raised and ready to fire; -- said of firearms, also, jocularly, of one prepared for instant action.
At half cock. See under Half.
Cock feather (Archery), the feather of an arrow at right angles to the direction of the cock or notch. --Nares. [1913 Webster]