adverb taking the 'to' particle, taru-adjective
noisily; clamorously; vociferously
Describes loud arguing, complaining, or heated discussion. Often used with 言う or 騒ぐ. The 々 form is more common.
彼らは喧々と議論を続けた。
They continued arguing noisily.
会議室から喧々たる声が聞こえてきた。
Clamorous voices could be heard from the meeting room.
Reduplication of 喧 (けん, 'noisy') with the iteration mark 々. The exact historical derivation is uncertain, but the form is conventionally associated with loud, contentious speech.