noun
Usage: usually capitalized A
: the bright central spot in the system of diffraction rings formed by an optical system with light from a point source (as a star)
noun
Usage: usually capitalized A
: the bright central spot in the system of diffraction rings formed by an optical system with light from a point source (as a star)
Webster's New International English Dictionary. Новый международный словарь английского языка Webster. 2012