diamond ring

Short definition from Wiktionary

Noun

1. 1
   Used other than figuratively or idiomatically: see diamond, ring.
2. 2
   By extension, an engagement ring, usually one given by a man to a woman.
3. 3
   An optical phenomenon visible during a moment of a solar eclipse when only a tiny part of the sun is not obscured by the moon, shining like a diamond in the ring of the sun’s corona.