megararityWiktionary 原文构词拆分mega-前缀(originally) Very large, great. · In the International System of Units and other metric systems of units, multiplying the unit to which it is attached by one million (106).+rarity词根/词干词源说明From mega- + rarity.释义（英文）名词 Noun(birdwatching, informal) An extremely rare bird for a particular locality.