/ Dictionary / Index C Crookes: Meaning and Definition of Find definitions for: Crookes Pronunciation: (krooks), [key] 1832–1919, English chemist and physicist: discovered the element thallium and the cathode ray. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: crookes (Thesaurus) crooked Crookes dark space 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