1.nounA thing whose name cannot be remembered; thingamajig, doohickey.
2.nounAny device or machine, especially one whose name cannot be recalled. Often either clever or complicated.
"He bought a neat new gadget for shredding potatoes."
3.nounAny consumer electronics product.
4.nounA sequence of machine code instructions crafted as part of an exploit that attempts to divert execution to a memory location chosen by the attacker.