A stud is a metal piece that sticks out, usually for decoration. You might have studs spelling out "Mom" on your leather jacket. Straight, simple earrings — a single pearl on a straight post, for instance — are also called studs.
There are a few meanings of stud that you should know if you are an equestrian or in construction. A stud is a male horse used for breeding, and it’s also slang for a macho he-man. If you want to hang a heavy mirror on a wall, you have to find the studs — the upright boards behind the wall — and hammer your nails into the studs, so the nails are anchored to something solid so they can support the weight of the mirror.