Definition from Wiktionary, the free dictionary
Ionian (not comparable)
- Relating to the Hellenic people of that name.
- Ionic, of Ionia, the ancient (ca 1100 BC) region including western Asia Minor and the adjacent Aegean Islands occupied by the Ionian people.
- Relating to Io, one of the moons of the planet Jupiter
Related terms 
A mode of music; played on the first note of a major scale. Also known as a major scale. Easy ! =D
Ionian (plural Ionians)