A dull grayish-brown color. The walls of the old barn were painted a dun color, blending perfectly with the surrounding landscape.
A demand for payment, especially a written one. He received a dun from the credit card company reminding him of his overdue balance.
A horse with a grayish-yellow coat and a black mane and tail. The cowboy rode a sturdy dun across the open plains.
A person who persistently demands payment of a debt; a persistent creditor. The shopkeeper became a constant dun, turning up every week to ask for the overdue amount.