Simple past tense and past participle of litter.(verb)
Covered in litter(adjective)
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Use "littered" in a sentence
"My major criticism of the model would be the amount of trash generated and littered from the individual packets."
"I just spent just a few minutes and found the word littered all over these websites."
"35Colonial settlers, regulated by both church and state, left a wider paper trail than Khoisan and slaves, though their paths remain littered with ambiguity."