Rowing team, e.g

• The planets, without Pluto
• Rowing team quorum
• Phases of the moon, say
• Full set of bicuspids, e.g.
• Two tetrads
• Slices in a pie, often
• Eight as one
• Santa's reindeer team, e.g
• Bits in a byte, e.g

The Collaborative International Dictionary Word definitions in The Collaborative International Dictionary
Octad \Oc"tad\, n. [Gr. ?, ?, the number eight.] (Chem.) An atom or radical which has a valence of eight, or is octavalent. A group of eight things.