What does "hackle" mean?

Additional senses

1. 2.One of the peculiar, long, narrow feathers on the neck of fowls, most noticeable on the cock, -- often used in making artificial flies; hence, any feather so used.
2. 3.An artificial fly for angling, made of feathers.
3. 4.To separate, as the coarse part of flax or hemp from the fine, by drawing it through the teeth of a hackle or hatchel.
4. 5.To tear asunder; to break in pieces. The other divisions of the kingdom being hackled and torn to pieces. Burke.