Sentence:  He ... began to descend to familiar questions, endeavouring to accommodate his discourse to the <WSD>grossness</WSD> of rustic understandings. The clowns soon found that he did not know wheat from rye, and began to despise him; one of the boys, by pretending to show him a bird's nest, decoyed him into a ditch; ... 
Meaning of the word marked with <WSD> tags:  Lack of refinement in character, behaviour etc.; coarseness.