taru-adjective, adverb taking the 'to' particle
slow; lagging; tardy
A literary or formal adverb/adjective describing progress that is very slow or delayed. Often used with として or たる to modify nouns or verbs.
交渉は遅々として進まなかった。
The negotiations made slow progress.
遅々たる歩みでは締め切りに間に合わない。
We won't meet the deadline at this sluggish pace.
Reduplication of 遅 (chi, 'slow'), forming a literary adverb/adjective. The exact historical derivation is uncertain, but the form follows classical Chinese-influenced patterns.