Sentence:  Now when the Master-at-arms noticed whence came that greasy fluid streaming before his feet, he must have taken it—to some extent wilfully, perhaps—not for the mere accident it assuredly was, but for the sly escape of a spontaneous feeling on Billy's part more or less answering to the <WSD>antipathy</WSD> on his own. 
Meaning of the word marked with <WSD> tags:  A feeling of dislike (normally towards someone, less often towards something); repugnance or distaste.