The act of grinding and hustling at the same time.

a verb formed from the words grind and hustle meaning to put in work or constant effort against harsh opposition.

Also a noun as in "the grustle" -- i.e. the rat race, the daily grind.

grind + hustle = grustle

Adjective used to describe a manly-ass voice, a voice so manly you can actually visualize the vein-throbbing mass of muscle emitting from those precious precious vocal chords.