1 A broad arc occasionally seen in the solar (as opposed to antisolar) sky during the darker half of civil twilight and, in principle, during nautical and astronomical twilight The afterglow chiefly consists of the purple light and bright segment 2 A stage of the alpenglow in which mountaintops are visibly colored by the purple light
The red glow persisting after extinction of the flame in fire resistance testing
in fire resistance testing, the red glow persisting after extinction of the flame