Sentence:  Clerfayt , driving , sees himself `` a volcano whose cone funneled down to hell '' ; the Briton Stirling Moss , one of the greatest virtuosi of all time , believes that ultra-fast road-circuit driving <WSD>is</WSD> an art form related to ballet . 
Meaning of the word marked with <WSD> tags:  have the quality of being; (copula, used with an adjective or a predicate noun)