A polite way of greeting a hearing impaired individual.
> "Look, there comes old Mrs. Danielson. The poor thing just can't hear anything anymore. Hi-Def!"
> "That filthy old man has been sitting on the street for so long that his darn ears have done rotted plumb off. Hi-Def!"
> "Hey that's Pete Townsend over there, isn't it? Hi-Def!"