Pentagon rhymes with:
polygon, aragon, argon, argonne, hexagon, hogan, octagon, paragon, polygon, agamemnon, aileron, alarcon, albashaun, amazon, antiphon, aragon, arbitron, argon, argonne, arton, autobahn, autobon, automaton, avalon, axon, babylon, betaseron, boron, capon, carillon, catchacan, celadon, cephalon, chapoton, christiaan, cimarron, comecon, crayon, d'aubuisson, dacron, digicon, dijon, distron, echelon, econ, emoticon, epsilon, erawan, ethicon, farrakhan, fenelon, germiston, greenspon, guslan, halon, hardymon, helicon, hexagon, hogan, huron, infotron, lexicon, liaison, lifson, littlejohn, logicon, magnetron, mahtan, marathon, memnon, meson, micron, midcon, monoszon, moron, narasimhan, neutron, nikon, nipon, nylon, oberon, octagon, oerlikon, olajuwon, oxdon, pantheon, paragon, parmesan, parthenon, phenomenon, photon, pi-meson, pion, planecon, polygon, polysilicon, pompon, positron, proton, pylon, qian, radon, radovan, ragavan, reveron, saamstaan, semicon, shihan, simion, siobhan, sirhan, slip-on, slobodan, symtron, technicon, telefon, teletron, tucson, upjohn, vanderlaan, videotron, walk-on, waylon, yukon