Hackle n. : A comb for dressing flax, raw silk, etc.; a hatchel.

Hackle n. : Any flimsy substance unspun, as raw silk.

Hackle n. : 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.

Hackle n. : An artificial fly for angling, made of feathers.

Hackle v. t. : To separate, as the coarse part of flax or hemp from the fine, by drawing it through the teeth of a hackle or hatchel.

Hackle v. t. : To tear asunder; to break in pieces.

Example:
which British Highland regiment wears a red Hackle?

Taxonomy
hackle, regiments, fusilier, SCOTS, feather bonnet, pipers, battalion, Royal blue, black hackle, red hackle, drummers, blue hackle, free encyclopedia, caubeen, infantry regiments, Red over white, St Patrick's blue, regimental.

Defination from the web:
hackle is a feather plume that is attached to the headdress. ... White hackle, as worn by the Royal Highland Fusiliers Battalion of the Royal Regiment of Scotland ... It may be that the black hackle of 1 SCOTS simulates the black-cock tail feathers originally worn in the 1904 ...