verb

cover or fill (something) with an untidy collection of things.

the room was cluttered with his bric-a-brac

litter,make untidy,make a mess of,mess up,throw into disorder,disarrange,jumble,be strewn about,be scattered about,make a shambles of,bestrew

noun

a collection of things lying about in an untidy state.

the attic is full of clutter