/ Dictionary / Index S slow neutron: Meaning and Definition of Find definitions for: slow' neu'tron Pronunciation: [key] — Physics. Physics. a neutron with low kinetic energy, esp. one slowed by the moderator in a nuclear reactor. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. slow-moving slowpoke Related Content Daily Word Quiz: eureka Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language