mullen
/ˈmʌlən/(also mulling, mullin, mullein) Chiefly British regional
noun
A headstall or bridle for a horse.
- mullen mouth saddlery noun a curved mouthpiece or bit, usually in the shape of a half moon, with the curve putting pressure on the horse's tongue..
Origin
Late 16th century. Origin uncertain; probably related to molan and mollet.