The definition of gizmo is slang for a gadget, especially an unnecessary one or one whose user can't remember its name.
An overly fancy corkscrew opener that does way more than you would ever need it to do is an example of a gizmo.
Slang any gadget or contrivance
Origin of gizmo; from uncertain or unknown; perhaps Spanish gisma, obsolete or dialect, dialectal variant, variety of chisme, trifle, jigger, ultimately ; from Classical Latin cimex, a bug
nounpl. giz·mos also gis·mos
A mechanical device or part whose name is forgotten or unknown; a gadget.
Origin of gizmoOrigin unknown.