taru-adjective, adverb taking the 'to' particle
in heaps; piled up; in piles
Describes things lying or being piled up in heaps, often with a sense of disorder or neglect. Used with と and often modifies verbs like 積む, 置く, or 死ぬ (corpses). Literary and somewhat formal.
Corpses lay in heaps on the battlefield.
Documents are piled up in heaps on the desk.
Standard kanji form using the common iteration mark 々.
Alternate kanji form without the iteration mark; less common but still used.
Reduplication of 累 (るい), meaning 'to accumulate' or 'pile up'. The exact historical derivation is uncertain, but the form is used in classical and literary Japanese.