1) Any noble gas, save helium 2) Bits in a byte 3) Crew, not counting the cox 4) Digit 5) Double quartet 6) Eight 7) Eight as one 8) Eight things 9) Eight united 10) Eight-PArt group 11) Eighter 12) Eighter from decatur 13) Eightsome 14) Ennead less one 15) Ennead minus one 16) Ensemble of eight 17) Figure 1) Eight 2) Eighter 3) Octet 4) Octonary 5) Ogdoad 
set of eight things
• (n.) An atom or radical which has a valence of eight, or is octavalent.
Oc'tad noun [ Greek ..., ..., the number eight.] (Chemistry) An atom or radical which has a valence of eight, or is octavalent. 
Type: Term Pronunciation: ok′tad Definitions: 1. An octavalent element or radical. Synonyms: octavalent