What's the meaning of “spike” in the context of “adrenaline spike”? how does it relate to the meaning of “dump” in the context of “adrenaline dump”? and which of the two is the correct version?
One refers to a spike in a measurement, or a sharp rise (often followed by a fall that may not be as sharp, but is clear). This is because such measurements would be drawn with a moving needle on paper, or otherwise graphed after the fact, and the spike looks like, well, a spike.
Thus, in an adrenaline spike the level of adrenaline in a person's system has risen sharply, and may not be sustained. We don't generally have ongoing measurement of things like that, but it means that if we did have that sort of ongoing measurement, the graph would show a visible spike.
An adrenaline dump is also a sharp rise in adrenaline, speaking figuratively as the adrenal glands "dumping" a load of adrenaline into your system all at once.
Both of those terms are 'correct', they are just looking at it from a different perspective.
If you're really being a purist about the terminology, a spike shouldn't be sustained, whereas a dump might be. In practice, they are used reasonably interchangeably, in my experience.
The term comes from the appearance on a graph. There are four main spikes in the following picture.
6 a : a pointed element in a graph or tracing
An adrenaline rush is when one experiences a sudden increase in the hormone adrenaline (also known as epinephrine). Apparently adrenaline dump has the same meaning, as I see from looking this up, though I’ve never heard dump used in this context. I guess spike (or surge) could be used as a synonym of one of those other words. However, as an American native speaker, the only one I’d say and that I think is most idiomatic is adrenaline rush. Also, if you’re asking what this means, it’s a biological process in response to fear and/or excitement. You might get this feeling while riding on a roller coaster or while skydiving, for example.
In practice, a spike in something really refers to any abrupt increase, even if the decrease afterwards is not abrupt. The visual image definitely is a time-series plot where you would see a spike-like projection if there was a rapid increase and a rapid decrease afterwards. But people are more concerned about the consequences of any rapid increase, so the term came to be used more broadly.
If you imagine a graph depicting the rate of change, rather than the level of the quantity, then an abrupt increase followed by a leveling off or a decline will always look like a spike. But I am not sure people thought it through in that much detail.