adverb
a great deal; very much; a lot
Emphatic adverb used to stress a large amount or degree, often in casual speech. Common with verbs like 食べる, 勉強する, or adjectives.
昨日はうんと寝た。
I slept a lot yesterday.
うんと勉強して、試験に合格した。
I studied very hard and passed the exam.
adverb
with great effort
Archaic use emphasizing strenuous effort. Rare in modern Japanese; replaced by expressions like 一生懸命 or 精一杯.
古文では「うんと努力する」のように使われた。
In classical texts, it was used like 'to strive with great effort'.
Onomatopoeic or mimetic origin, likely from the sound of forceful exhalation or effort. The exact derivation is uncertain.