A projecting starched frill worn round the neck, characteristic of Elizabethan and Jacobean costume. (Oxford Dictionaries)
A projecting or conspicuously coloured ring of feathers or hair round the neck of a bird or mammal. (Oxford Dictionaries)
A large, stiff collar with many folds, worn in Europe in the 16th and 17th centuries, or a circle of hair or feathers growing round the neck of a bird or animal. (Cambridge Dictionary)
A large round collar of pleated muslin or linen worn by men and women of the late 16th and early 17th centuries. (Merriam – Webster)
Ruff clothing. Wikipedia.
Ruff vs rough. Homophones.