taru-adjective, adverb taking the 'to' particle
well-ordered; in good order; orderly
Obsolete term describing a state of being neatly arranged or well-organized. Used as a taru-adjective or adverb with と.
古い文献には「整々たる陣容」といった表現が見られる。
In old texts, one can find expressions like 'a well-ordered battle formation'.
The phrase 'items arranged in good order' is hardly used today.
Modern equivalent meaning 'orderly' or 'systematic', commonly used as a taru-adjective or adverb.
The exact derivation is uncertain; the kanji 整 means 'arrange' or 'order', and the reduplication suggests an emphatic or adverbial form.