Combustion
A planet is combust when it comes too close to the Sun and is, in the tradition, 'burned' by its light.
What it is
When a planet gets within a few degrees of the Sun it disappears in the Sun's glare. Classical astrology calls this combustion. Each planet has its own range, roughly 8 to 17 degrees.
How the tradition reads it
A combust planet is read as weakened: its themes are present but overshadowed. A combust Mercury, for example, is read as muddled communication; a combust Venus as values that are hard to see clearly.
In AstroFinex
Combustion is part of how the engine judges whether a planet is working or afflicted, which then feeds the stance.