Spur generally means a short spike or spiked wheel that attaches to the heel of a horse rider’s boot and it is used to urge a horse forward. It is generally a U- shaped thing which is sharp enough for pinching horse to go forward.  It slips over and straps to the heel.  It has a blunt, pointed, or rolled in it. Blunt means thing having an obtuse, thick    or dull edge or point and it must stay rounded, not sharp. You can give an example of it using a normal pencil.
Ornithology describes that spur means a stiff, usually sharp, horny process on the leg of various birds. Especially the domestic rooster. It can also be found on the bend of the wing, as in jacanas and screamers. 
Spur is also means a track of an animal, as an otter, a spoor. It has so many meanings and works with to do.  Sometimes a spur is also meant a wall that crosses a part of a rampart and joins to an inner wall. It is also a sparrow, A curved piece of timber serving as a half to support the deck where a whole beam can not be placed, A brace strengthening a post and some connected part, as a rafter or crossbeam; a strut, An implement secured to the heel, or above the heel, of a horseman, to urge the horse by its pressure. Modern spurs have a small wheel, or rowel, with short points. Spurs were the badge of knighthood.

It can also mean some other stuff. A mountain that shoots from any other mountain, or range of mountains, and extends to some distance in a lateral direction, or at right angles or any projecting appendage of a flower looking like a spur. It can have these five meanings also- A verbalization that encourages you to attempt something, Any sharply pointed projection, Tubular extension at the base of the corolla in some flowers, A sharp prod fixed to a rider’s heel and used to urge a horse onward, A railway line connected to a trunk line. When spur is said as a verb then the meanings run a long way. Let’s have some example. It can mean Incite or stimulate, Give heart or courage to, Strike with a spur, Goad with spurs, and Equip with spurs.
In short we can tell that spur actually means a lot of things, I hope all understood.