/ Dictionary / Index C Crookes dark space: Meaning and Definition of Find definitions for: Crookes' dark' space" Pronunciation: [key] — Physics. Physics. the dark space between the cathode glow and the negative glow in a vacuum tube, occurring when the pressure is low. Also called Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. Crookes crookesite Related Content Daily Word Quiz: fresco Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language