Tousle is a verb that means to make hair messy or untidy. 

Derived from German and related to the word ‘tussle,’ our word of the day has been with us since the late Middle English period. Here’s an example:

Just before entering the bar, I tousled my hair to make sure I looked appropriately rugged. But the problem is I have so little hair left, I’m not sure anybody would notice a change.