Is yugāvatāra a well-defined term in the scriptures or just a pet name assigned by devotees to their Ishta-deva (worshipable deity) whom they consider to be the most important for that yuga?
Are they the same in various mahāyugas, or changing, like in one Kali-yuga Buddha is the principal, in another — Kalki?
Šrī Satya Sai and Šrī Rāmakrišna wear the title and Šrī Krišna Caitanya is also called "yugāvatāra" by followers, all related only to this particular Kali-yuga. Is there a more complete list?