1. A term that originated with Extreme Programming (XP) that is used to refer to work whose primary purpose is explore potential solutions or otherwise gather information. A way to acquire knowledge when the situation at hand has uncertainty as to the proper or good way to proceed forward. 2. In agile development, a spike can be represented as a product backlog item who primary output is the knowledge obtained by performing the spike work.  3. Some people use the term spike to refer to an end-to-end architectural prototype. The visual metaphor is: Imagine you had a physical spike in one hand and a hammer in the other hand. Take the hammer and hit the spike so that it vertically pierces all layers of the architecture (e.g., GUI, middle tier, database).