A word that can take the place of any one noun.
While working on his hot ride, John Doe reaches for his screw driver but can't reach it. He says to Tony "Eh Tony, hand me the uh.... thingamajigger" Tony-"oh, you mean the screwdriver?" "Yeah, that's it"
So I ran over a thingamajigger on the way home from work. It's hair got caught all up in my tires. Sick.