Wiktionary
balls-deep
adv. 1 (context vulgar English) With the penis fully immersed in an orifice, more often the anus or vagina than the mouth. 2 Fully committed to a situation.
Usage examples of "balls-deep".
He sank into her balls-deep, once, twice, three times more, then, teeth gritting, groaned as he spurted his cum deep inside of her.