Meaning of the Sanskrit Word: vajrena

  vajrena—with the thunderbolt    SB 6.12.3, SB 6.12.25
  vajrena—by the thunderbolt    SB 6.12.32, SB 8.11.6
  vajrena—by his thunderbolt    SB 6.18.62
  vajrena—with his thunderbolt    SB 8.11.18

Can't find any compound Sanskrit words containing vajrena.