treb·u·chet 
(trĕb′yə-shĕt) also treb·uc·ket (-ə-kĕt)
(trĕb′yə-shĕt) also treb·uc·ket (-ə-kĕt)n.
A medieval catapult for hurling heavy stones, often employing a long sling.
[Middle English, from Old French, from trebucher, to overthrow : tre-, over (from Latin trāns-; see TRANS-) + but, trunk of the body (of Germanic origin).]
trebuchet