वज्रिबाहुविसर्जितः released from thunderbolt hurled by the arm of Indra, वज्रःइव like thunderbolt, दुर्धर्षः difficult, कृतान्तःइव capable of bringing to an end, अवार्यः prevent, सः that, रावणोरसि into Ravana's chest, न्यपतत् penetrated

Like the thunderbolt hurled by the arm of Indra, difficult to obstruct, capable of bringing life to an end, that arrow released by Rama penetrated into Ravana's chest.