Princeton's WordNet

1. radium, Ra, atomic number 88(noun)

   an intensely radioactive metallic element that occurs in minute amounts in uranium ores

   Synonyms:
   right ascension, radium, celestial longitude, atomic number 88

2. Ra, Re(noun)

   ancient Egyptian sun god with the head of a hawk; a universal creator; he merged with the god Amen as Amen-Ra to become the king of the gods

   Synonyms:
   right ascension, ray, radium, celestial longitude, atomic number 75, atomic number 88, rhenium

3. right ascension, RA, celestial longitude(noun)

   (astronomy) the equatorial coordinate specifying the angle, measured eastward along the celestial equator, from the vernal equinox to the intersection of the hour circle that passes through an object in the sky; usually expressed in hours and minutes and seconds; used with declination to specify positions on the celestial sphere

   Synonyms:
   right ascension, radium, celestial longitude, atomic number 88