Definitions

1. noun

a thing whose name is unknown or forgotten, especially a tool or device

“She rummaged through her grandmother’s attic, searching for the whatsis used to peel potatoes.”

2. interjection

an expression of curiosity or puzzlement

“What’s that thingamajig, whatsis, or a whatchamacallit?”

3. adjective

unknown or unidentifiable

“The whatsis in her kitchen was covered in dust and couldn’t be found in any manual.”