Ichidan verb, Intransitive verb
to be clear (of a sight, sound, colour, etc.); to be bright; to be vivid; to be crisp
満月が空にさえている。A full moon is shining bright in the sky. to be clear-headed; to be alert; to be on the ball; to be wide awake
to look upbeat; to be perky; to be cheerful
often as 冴えない
to master (a skill); to excel at; to cleanly execute
to be satisfying
often as 冴えないsee 冴えない
to become frigid; to become intensely cold
original meaning; now somewhat old-fashioned
Also written 冱える【さえる】