or who·sis

[ hoo-zis ]
/ ˈhu zɪs /

noun, plural whoo·sis·es. Informal.

an object or person whose name is not known or cannot be recalled: It's the whoosis next to the volume control.
a person or thing considered typical or illustrative: the usual paragraph about the party given by Mme. Whoosis.

Origin of whoosis

First recorded in 1920–25; alteration of phrase who's this
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019