/mas"euhn/
a white disk on which a series of concentric gray circles appear to vanish intermittently when the disk is rotated, used for testing a person's fluctuation of attention and visual threshold.
/mas"euhn/
a white disk on which a series of concentric gray circles appear to vanish intermittently when the disk is rotated, used for testing a person's fluctuation of attention and visual threshold.
Random House Webster's Unabridged English dictionary. Полный английский словарь Вебстер - Random House . 2012