Sentence:  "Masks!" exclaimed I; "why, it isn't carnival time, is it?" "To be sure 'tis," replied he, "dis is <WSD>Mardi gras</WSD>, de gayest of de gay days. Noting but pleasure, and fun, and hosh-posh." 
Meaning of the word marked with <WSD> tags:  The last day of a carnival, traditionally the celebration immediately before the start of Lent when joy would be out of place for Christians.