adverb taking the 'to' particle
strongly; violently; with all one's strength
Describes a forceful, vigorous action, often with a sudden or intense nuance. Used with と before a verb.
彼はむんずと相手の腕をつかんだ。
He grabbed the opponent's arm with all his strength.
むんずと荷物を持ち上げた。
She lifted the luggage forcefully.