/ Dictionary / Index F first-line: Meaning and Definition of Find definitions for: first-line Pronunciation: (fûrst'līn'), [key] — adj. available for immediate service, esp. combat service: first-line troops. of prime importance or quality. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. first light firstling 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