Avatāra. This Sanskrit term means literally "descent" and is frequently used of the manifestation of a deity. Although certain lists are to be found in Indian literature designating the gods who manifest themselves in human form, the concept is so pervasive that it has become what might be called a recognized principle. Any outstandingly holy man or great sage is readily regarded, in popular Hinduism at any rate, as a manifestation of deity. Any person of the caliber of an Albert Schweitzer or a Mother Teresa might be so regarded, no less than may Gandhi and other exemplars of the same spirit within the Indian framework. In the Hindu context, therefore, the concept of such avatars of deity is not at all a counterpart to the Christian concept of Christ as God incarnate, although there are superficially common elements in the two notions.

Geddes MacGregor, Dictionary of Religion and Philosophy, New York: Paragon House, 1989

avatāra: Descent, entering, entrance.

Sarvastivada Abhidharma, Sanskrit-English Glossary, by Bhikkhu KL Dhammajoti

ava-tāra m. (Pāṇ. 3-3, 120) descent (especially of a deity from heaven), appearance of any deity upon earth (but more particularly the incarnations of Vishṇu in ten principal forms, viz. the fish tortoise, boar, man lion, dwarf, the two Rāmas, Kṛishṇa, Buddha, and Kalki MBh. xii, 12941 seqq.)
• any new and unexpected appearance Ragh. iii, 36 & v, 24, &c., (any distinguished person in the language of respect is called an Avatāra or incarnation of a deity)
• opportunity of catching any one Buddh
• a Tirtha or sacred place L
• translation L

Sanskrit-English Dictionary, by M. Monier William