資料來源 : Webster's Revised Unabridged Dictionary (1913)

Topple \Top"ple\, v. i. [imp. & p. p. {Toppled}; p. pr. & vb. n.
   {Toppling}.] [From {Top} summit.]
   To fall forward; to pitch or tumble down.

         Though castles topple on their warders' heads. --Shak.

資料來源 : WordNet®

toppling
     adj : falling over as if from top-heaviness or lack of support; "a
           toppling pile of books"; "toppling empires"