1. To depart for or begin traveling to (some place). Make sure you eat a good breakfast before you strike off! I'm striking off for New York tomorrow to attend a business meeting.

2. To cause someone to fall off (of something) by hitting, kicking, pushing, or knocking into them. In this usage, a noun or pronoun is used between "strike" and "off." The jouster struck his opponent off his horse. He struck the lamp off the table with the baseball.

3. To split, sever, or break off something (from something else) with a forceful blow. In this usage, a noun or pronoun is used between "strike" and "off." He struck off a piece of concrete with the swing of his hammer. They spent the day striking chunks of ice off the giant block.