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1.
A word that can be produced by the same keystrokes as another word while using the T9 text entry method in a cell phone.
Some T9onyms like eat and fat can be funny, but usually they are annoying and confusing while texting.
by Ichserbe March 04, 2009
 
2.
The relationship between two words which have exactly the same keystroke series when texting while using a predictive text program.

They are distinctly different from words which interchange simply due to a typo and auto incorrect.
Girl in text: Good night! Love you!
Guy in text back: Hoof night! Knud you tom!
Girl in text: Oh T9onyms! Like a secret code! You're so funny!

Mom in text: When will you be good?
Son in text: What? ...Always?
Mom in text: Don't tall back! Bond gone nox!
Son in text: I think you are having a T9onym attack...
by KRA2008 June 23, 2011