adverb taking the 'to' particle, taru-adjective
triumphantly; proudly; smugly
Describes a self-satisfied, gloating manner, often with a visible air of pride. Used adverbially with と or as a たる adjective.
彼は試験に合格して、得々としている。
He passed the exam and is looking very pleased with himself.
得々とした顔で賞状を受け取った。
He received the certificate with a smug look on his face.
Kana spelling; used when the kanji is avoided or for emphasis.
Reduplication of 得 (とく, 'profit, gain'), emphasizing a state of having gained an advantage. The exact historical derivation is uncertain, but the form suggests an adverbial/adjectival use meaning 'in a state of having gained'.