A volume spike is a single candle that trades far more than usual: more than 3x the average volume of the last 20 bars. A spike like that means something notable happened on that bar, whether news, a large order, or heavy breakout participation.
In plain terms
A lot of people suddenly traded on one candle. It tells you "pay attention", but not on its own which way price will go.
What triggers it
The candle's volume must be more than 3x the 20-bar average volume. The direction is neutral by default, because volume alone says something happened, not which way it resolves. If that same candle also produced a move bigger than 0.5%, we label the direction by whether it closed up or down.
How Signalix scores strength
The base score is 2 out of 5, because volume by itself is informational rather than directional. We add a point when the candle's price move is larger than 1%, which shows the heavy volume actually translated into a real move.
What it works best with
Volume spikes are most useful as confirmation for another signal. Treat one as a corroborator for a breakout, a sweep, or a structure break, rather than as a standalone reason to act.