9-letter word - NAVIGATOR
Some other words of five letters or more containing the hub letter R:
agora, antra, aorta, argon, argot, atria, grain, grant, griot, groan, groat,
groin, intro, naira, noria, organ, raita, ratio, riant, riata, taira, tiara, train,
varan, vigor (US), virga, angora, organa, rating, ration, raving, roving,
trigon, virago, aviator, orating, vagrant, variant.