1 a: a fire or blaze of light used especially to signal, illuminate, or attract attention; also: a device or composition used to produce such a flare 2: an unsteady glaring light b:solar flare; also: a sudden increase and decrease in the brightness of a star often amounting to a difference of several magnitudes 3 a: a sudden outburst (as of excitement or anger) b:flare-up 3 4 a: a spreading outward; also: a place or part that spreads b: an area of skin flush 5: light resulting from reflection (as between lens surfaces) or an effect of this light (as a fogged or dense area in a photographic negative) 6 a: a short pass in football thrown to a back who is running toward the sideline b: a weakly hit fly ball in baseball <a flare into short right field> 7plural: pants that flare toward the bottom