1 also litter up [transitive]
if things litter an area, there are a lot of them in that place, scattered in an untidy way:
Clothes littered the floor.
litter something with something
The desk was littered with papers.
if something is littered with things, there are a lot of those things in it [= be full of something]:
Recent business news has been littered with stories of companies failing.
3 [intransitive and transitive]
to leave waste paper, cans etc on the ground in a public place
4 [intransitive] technicalHBA
if an animal such as a dog or cat litters, it gives birth to babies