The dry leaves can easily combust if exposed to a spark.
To cause something to catch fire and burn. The chemist carefully measured the substances to ensure they would not combust during the experiment.
To undergo a chemical reaction that produces heat and light. The fuel will combust when mixed with oxygen in the engine.
(figurative) To become suddenly and violently emotional, especially with anger or excitement. If he finds out they broke his trophy, he's going to combust.