Ratnakūṭa (Sanskrit, heap of jewels). A compilation of early Mahāyāna sūtras. The work comprises 49 sūtras, some of particular importance such as the Kāśyapa-parivarta, the Akṣobhya-vyūha, the Sukhāvatī-vyūha, the Śrī-mālā-devi-siṃhanāda, and the Raṣṭrapāla-paripṛcchā. Though the entire corpus is only available in Chinese and Tibetan translation, copies of the Sanskrit original texts do survive for some items.

A Dictionary of Buddhism, Oxford University Press, 2003, 2004 (which is available in electronic version from answer.com)

○kūṭa m. N. of a mountain L.
• of a Bodhi-sattva Buddh.
• n. N. of an island Kathās.
• -sūtra n. N. of a Buddhist Sūtra wk

Sanskrit-English Dictionary, by M. Monier William

【梵】ratnakūṭaḥ
【梵】रत्नकूटः【中】寶積
【藏】rin chen rtsegs pa

Mahāvyutpatti - DDBC version