litter up

litter (something or some place) up

To make something or some place very messy or untidy. I hate the way he litters up his desk with papers and dirty plates—it just looks really unprofessional. The room wasn't clean for more than an hour before the kids had littered it up with toys and bits of food.
See also: litter, up

litter something up

to mess something up with litter, trash, possessions, etc. Who littered this room up? Who littered up this room?
See also: litter, up