Join Us On

Browse Dictionary Browse Thesaurus

Get our free apps!iPhone•iPad•Android

Dictionary

I/O

abbreviation

Definition of I/O

input/output

Next Word in the Dictionary: ioaPrevious Word in the Dictionary: IoAll Words Near: I/O

What made you want to look up I/O? Please tell us where you read or heard it (including the quote, if possible).

Put-downs with flair

How to use a word that (literally) drives some people nuts.

Test your vocab with our fun, fast game

Ailurophobia, and 9 other unusual fears

Join Us

Merriam-Webster
on Facebook

Merriam-Webster
on Twitter

Bookstore: Digital and Print

Merriam-Webster references for Mobile, Kindle, print, and more.

See All

Other Merriam-Webster Dictionaries