But once his art in senseless pride Upon the mightiest saint he tried, Agastya’s self, and caused him taste The baited meal before him placed. Vátápi, when the rite was o’er, Would take the giant form he wore, But Saint Agastya knew his wile And checked the giant with smile.

In plain words: Rama recalls a demon named Vatapi who tricked holy men by becoming their food and then bursting out of them. When he tried it on the great sage Agastya, Agastya saw through the trick and calmly defeated him.