Mammoth Uncensored Word List:
57 words ending with x, 9 letters long

aboideaux aboiteaux antihelix autoindex bisectrix canarypox candlewax cheesebox decomplex dictatrix directrix disclimax dorsiflex earthflax eightysix executrix fellatrix flambeaux geococcyx gogglebox gravadlax heterodox homoeobox letterbox mediatrix metroplex monkeypox multiplex neocortex nonconvex nonduplex nonmatrix pepperbox pigeonpox piscatrix pompholyx prehallux prepollex priedieux prothorax rattlebox religieux retroflex shadowbox sluicebox spondulix strongbox subclimax subcortex submatrix superflux terminvox testatrix tinderbox tuckerbox unperplex windowbox