How do I turn off/disable my trackpad on a MacBook Air?
To turn off the track pad you’ll need to attach a mouse or wireless trackpad but you don’t need to use it. 

To turn off the trackpad when a mouse is connected:


From the  Apple menu go to System Preferences
Click Accessibility 
Select Mouse and Trackpad on the left 
Select “Ignore built-in trackpad when mouse or wireless trackpad is present”