In plain words
Alas! Death walks behind me, mouth gaping like a cave to swallow me, closing in again and again, like a snake behind a frog. Hari, salutation to Nārāyaṇa.
Word for word
Alas! Kṛtānta, his mouth split open like a cave to devour, walks behind me here, coming on again with force, like a snake behind a frog. Hari, salutation to Nārāyaṇa.