means Having a lively, sharp, invigorating quality — full of flavor, energy, or piquancy.

from From 'zest,' which entered English in the 1600s from the French 'zeste,' meaning the peel of a citrus fruit — that fragrant, oily skin you grate over a dish. Because the peel carries the brightest, most aromatic punch of an orange or lemon, 'zest' came to mean any sharp, exciting flavor, and then any keen enjoyment of life. The '-y' adjective ending followed, turning the noun into a description of anything that crackles with that same citrus-bright liveliness. The deeper roots of the French word are murky, but the citrus-peel sense is solid.