whatchamacallit

But I had to come down with whatchamacallit so that I wouldn’t have to team up with Katie for the working-with-a-partner project in social studies this semester.

I had an array of belts, clamps and whatchamacallits.

I had no doubt she was going to become the premier physician-scientist of whatchamacallit.

When you throw the thing to the whatchamacallit, and the other team catches it instead, does that make you feel sad?

To be the whatchamacallit of something or other.