1. To splash or spatter up the length of something. Mud splattered up my pantlegs during the hike. The storm kept getting worse, and huge roiling waves splattered up the sides of the cliffs.

2. To cause some liquid splash or spatter up the length of something. In this usage, a noun or pronoun is used between "splatter" and "up." Be careful out there—you're splattering mud up the side of the house! The bacon splattered grease up the wall behind the stove as it cooked in the pan.