[n] a sudden happening that brings very good fortune [n] an especially rich vein of precious ore
boom, manna from heaven
abundance, affluence, ample sufficiency, ampleness, amplitude, avalanche, bountifulness, bountiousness, bumper crop, copiousness, cornucopia, Eldorado, extravagance, exuberance, fertility, flood, flow, foison, font, fount, fountain, full measure, fullness