Mammoth Uncensored Word List:
42 words ending with x, 10 letters long

anticlimax antireflux bordereaux chalumeaux chatterbox chickenpox circumflex coadjutrix contraplex crossindex dominatrix ectocervix gaspereaux generatrix glycocalyx googolplex groundprox hemothorax inheritrix initiatrix mesothorax metathorax moderatrix nanosyntax nectocalyx noncomplex oropharynx prattlebox precentrix protectrix quadratrix quadruplex separatrix seventysix spectatrix squeezebox subbureaux superhelix thunderbox trisectrix trousseaux unorthodox