swelter UK /ˈswɛl.tə/US /ˈswɛl.tɚ/verb 3noun 1forms 3 verb3 •To suffer terribly from intense heat. •To perspire greatly from heat. •To cause to faint, to overpower, as with heat.It was so rare a piece of fun To see the swelter'd cattle run — 1796 noun1 •Intense heat.The summer swelter did not relent until late in September, most years. formssweltered · sweltering · swelters