flare

To burn or shine with a sudden, bright, unsteady light.

"The match flared briefly in the dark."

To gradually widen outwards, especially at the bottom or end.

"The skirt flared out elegantly."

To suddenly erupt or intensify, often referring to anger or an illness.

"His temper flared up again."

A device producing a bright flame or light, used as a signal.

"They fired a red flare for help."