If you are annoyed by the Autocorrect on a Mac, here is the solution you are looking for. This trick will teach you how to disable autocorrect of spelling on a Mac. Autocorrect is enabled by default under the Yosemite OS X Apples newest version of its desktop operating system. Therefore, the steps youd need to perform while using past versions of OS X may vary from version to another.
Go to Spotlight by clicking on the magnifying glass icon in the upper right-hand corner of your desktop.
Then type keyboard, and click the first result which appears and will lead you to Yosemites Keyboard settings in the system preferences menu.
Click on the Text tab at the top of the window, and uncheck the box labeled Correct spelling automatically.
This is the final step, OS X will no longer try to correct your spelling.