noun
cootie
KOO-tee/ˈkuːti/
An imaginary germ or source of contamination in children's play.
The children pretend that a cootie can pass through a fingertip touch.

Etymology
From a real body louse, cootie became a child’s imaginary source of contamination.
More examples
- She crossed her fingers to ward off cooties.
- The playground game involved chasing away imaginary cooties.
Forms
cootie · cooties
Similar words
- germ
- Usually names a real microscopic organism.
- contamination
- Is the broader idea of becoming unclean or affected.