(uncountable) A confused disordered jumble of things.

(uncountable) Background echoes, from clouds etc., on a radar or sonar screen.

(countable) Alternative form of clowder (“collective noun for cats”).

(mathematics) A Sperner system.

To fill something with clutter.

To make a confused noise; to bustle.

To utter words hurriedly, especially (but not exclusively) as a speech disorder (compare cluttering).