io

exclamation1

1. •
   (rare) An exclamation of joy or triumph.

   • Do as thou wilt, as a great god can, O Pan! Io Pan! Io Pan! Io Pan Pan! I am awake In the grip of the snake. — 1913

noun1

1. •
   A type of moth, the io moth.

   • These lines appear to serve as roadways or guides to any stragglers that may have hung back for some reason known only to an io. — 1936

adjective1

1. •
   Abbreviation of intraosseous.

noun6

1. •
   Initialism of input and output.
2. •
   Initialism of intelligence officer.
3. •
   Initialism of international organization.
4. •
   Initialism of indirect object.
5. •
   Initialism of incident officer.
6. •
   (Singapore) Initialism of investigation officer.