thingummy (
http://definr.com/thingummy)
n : something whose name is either forgotten or not known [syn:
dohickey,
dojigger,
doodad,
doohickey,
gimmick,
hickey,
gizmo,
gismo,
gubbins,
thingamabob,
thingumabob,
thingmabob,
thingamajig,
thingumajig,
thingmajig]