Gadget (computer science)
In computational complexity theory, a gadget is a subunit of a problem instance that simulates the behavior of one of the fundamental units of a different computational problem. Gadgets are typically used to construct reductions from one computational problem to another, as part of proofs of NP-completeness or other types of computational hardness.
Source: Wikipedia — Gadget (computer science) (CC BY-SA 4.0)