सः मारुतात्मजः that son of the Wind god, प्रभावात् by his prowess, सुमहाकायः of a huge body, भूत्वा being, शब्देन by the sound, लङ्काम् Lanka, पूरयन् while filling, धृष्टम् roughly, अस्फोटयामास started patting (his arms)

Hanuman heaved his body huge with his prowess and patted his arms loudly filling the city of Lanka with that terrible sound.