To spike a foe usually means using an important quantity of resources for a single fight (usually a boss).
To its larger extent, these resources could be anything :
- Monster Xp (for level-up's, see popcorn)
- Exploration (for longer the average regen-fighting)
- Conversion points (when it provides a temporary effect)
- Death protections
- Blood pools
- Gold (when it provides a temporary effect, such as the crystal ball)
- well anything else you can make use of, and that is in limited quantity...
The devs have given the most concise explanation of spike with: "Draw a graph of damage output, if it spikes, that's a spike.", even though it was the players who came up with the term when trying to map out the different approaches to playing the game. The devs do advise against overusing the term as it's not specific enough on it's own. Even the people who came up with it agree, but find it usefull in discussions about theory and moments where a particular spike doesn't have a catchy nickname yet and has to be described by how it's performed.
An idea behind "spiking" is that a run cycles through 2 phases:
- The setup, during which the player explores the dungeon and hoards/saves various resources
- The execution, during which the player spikes tough opponents, boss or bosses, consuming an important part of these resources.