/ Dictionary / Index N nanosecond: Meaning and Definition of Find definitions for: nan•o•sec•ond Pronunciation: (nan'u-sek"und, nā'nu-), [key] — n. one billionth of a second. Abbr.: ns, nsec Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: nanosecond (Thesaurus) nanoplankton nanotechnology Related Content Daily Word Quiz: banshee Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language