1. To tumble or plummet over the edge (of something tall). The weather vane came toppling off the roof during the storm. Please don't get so close to the edge of that cliff—one strong gust of wind, and you'll go toppling off!
2. To cause someone or something to tumble or plummet over the edge (of something). In this usage, a noun or pronoun is used between "topple" and "off." Watch where you're walking—you nearly toppled that bucket off of the roof! He charged into the mutineer and toppled him off the boat.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
topple off (of) somethingand topple from something
to fall off the top of something very tall. (Of is usually retained before pronouns.) Careful there! You might topple off of that wall. I didn't get too close to the edge, because I was afraid of toppling off. She toppled off the wall. The vase toppled from its shelf in the quake.
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs. © 2002 by The McGraw-Hill Companies, Inc.