Can I disable auto-correction of a single word on OS X?
Yes you can do it.  


Go to System Preferences > Keyboard > Text.  
Click the + sign on the bottom left to add a new text replacement.
In the Replace column, put the word you want OS X to stop autocorrecting (no spaces are allowed).
In the With column, put the exact same word you put in the Replace column.


Voila.  You're done.

This has worked flawlessly for me every time.