Sentence:  Landesco thought him `` just a superior sort of plugugly '' but he <WSD>was</WSD> , in fact , with his aggression and hostility , and nerveless indifference to risking or administering pain , a casebook psychopath . 
Meaning of the word marked with <WSD> tags:  have the quality of being; (copula, used with an adjective or a predicate noun)