airship, dirigible
['rule, ruler', 'hammerhead, hammerhead shark', 'breakwater, groin, groyne, mole, bulwark, seawall, jetty', 'jean, blue jean, denim', 'backpack, back pack, knapsack, packsack, rucksack, haversack', 'breastplate, aegis, egis', 'ice bear, polar bear, Ursus Maritimus, Thalarctos maritimus']