N-/ma-, -um-, mag-, magsi-
-un, -an, pagsi--un/pag--un
(For a body part) to strike or be struck against s.t. else [-an]; to strike with an instrument against s.t. else [-un].
The -un imp. focuses on the goal. The -an imp. focuses on the object that you are striking against s.t. else. The pagsi--un/pag--un imp. focuses on both objects that are banged together.
I struck his head against that tree.
While I was walking my foot struck a rock.