taru-adjective, adverb taking the 'to' particle
easily; simply; without difficulty
Formal or literary adverb used to describe an action done with ease, often in a somewhat elevated or written style. Typically appears as 易々と.
He solved the difficult problem with ease.
They easily defeated the enemy.
Variant kanji spelling without iteration mark; less common but still encountered.
Reduplication of the kanji 易 (easy), forming a literary adverb. The reading いい is an on'yomi-based reduplicative pattern.