dome, hood, roof

capsule, case, casing, covering, housing, jacket, sheath, shell

baseball cap, beret, billycock [British], biretta, boater, bonnet, bowler, calotte, capuche, casque, castor, cloche, cocked hat, cowboy hat, cowl, derby, fedora, fez, garrison cap, hard hat, helm, helmet, high hat, homburg, hood, kepi (also képi), kufi, leghorn, miter (or mitre), nightcap, opera hat, overseas cap, panama, picture hat, pillbox, plug hat, porkpie hat, service cap, shako, silk hat, skimmer, skullcap, sombrero, sou'wester, Stetson, stocking cap, stovepipe, sunbonnet, tam, tam-o'-shanter, ten-gallon hat, top hat, topper, toque, tricorne (or tricorn), turban, zucchetto

warbonnet