1. A long metal nail.
2. A sharp-pointed projection along the top of a fence or wall.
3. Any long sharp-pointed object used as a fastener or holder.
4. Sharp point on the sole of shoe worn by athletes; spikes provide greater traction.
5. A long sharp-pointed implement (wood or metal).
6. A transient variation in voltage or current.
7. (Botany) An indeterminate inflorescence bearing sessile flowers on an unbranched axis.