before vowels meg-, word-forming element often meaning "large, great," but in physics a precise measurement to denote the unit taken a million times (megaton, megawatt, etc.), from Greek megas "great, large, vast, big, high, tall; mighty, important" (fem. megale), from PIE root *meg- "great." Mega began to be used alone as an adjective by 1982.
"reproductive body in flowerless plants corresponding to the seeds of flowering ones," 1836, from Modern Latin spora, from Greek spora "a seed, a sowing, seed-time," related to sporas "scattered, dispersed," sporos "a sowing," from PIE *spor-, variant of root *sper- "to spread, sow" (see sparse).