Upaśānta (Upasanta) is one of the Aṣṭottara (Ashtottara) Sahasranāma (Sahasranama) of God Śiva (Siva). In his Bhāratakaumudī (Bharatakaumudi) ṭīkā (tika), while explaining the meaning of ‘Upaśānta’, Haridāsa Siddhāntavāgiśa (Haridas Siddhantavagish) has said, —
Rudra Śiva (Siva) gets angry very quickly, but he can also be calmed down with little effort. So he is known as Upaśānta.
One meaning of Upa can be ‘in proximity’ or ‘near’. Coming close to his divine grace, one have the blessed feeling of calmness — in this sense as well, Śiva can be addressed as Upaśānta.