Any particularly arbitrary or obscure command that one must mutter at a system to attain a desired result. Not used of passwords or other explicit security features. Especially used of tricks that are so poorly documented that they must be learned from a wizard. "This compiler normally locates initialised data in the data segment, but if you mutter the right incantation they will be forced into text space."
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Nearby terms: in-band signaling « in-band signalling « inc « incantation » include » include war » inclusive