hypergolic
Igniting spontaneously upon contact with an oxidizer.
Although the LF₂-LH₂ cryogenic combination is hypergolic, the toxicity of the fuel and the products of combustion have made the use of this system impractical. In general, the commonly used hypergolic propellants are considered conventionally storable, that is, they do not need special refrigeration equipment to keep them liquid.
Involving such a hypergolic agent.
The chemical reaction range of hypergolic mixtures varies from slow and barely visible to an instantaneous and highly visible explosive force.
Where it comes from
From Ancient Greek ὑπέρ (hupér) + ἔργον (érgon, “work”) + -ol + -ic, after the model of German Hypergol and hypergolisch. Equivalent to hypergol + -ic.
Adapted from the Wiktionary entry hypergolic (CC BY-SA 4.0).