Sentence:  Do you feel a creeping, shrinking sensation, Watson, when you stand before the serpents in the Zoo, and see the <WSD>slithery</WSD>, gliding, venomous creatures, with their deadly eyes and wicked, flattened faces? Well, that's how Milverton impresses me. 
Meaning of the word marked with <WSD> tags:  That slithers; that moves like a snake.