Before you being reading the next chapters, use either context clues or a dictionary to match the correct definition with the words in bold.
(idiomatic)-Poirot says that the phrase Ratchett used to dismiss the conductor was "a perfectly idiomatic phrase . . . not one that a man knowing only a few words of French would have selected."
(deprecating)- When M. Bouc jumps to a conclusion, Poirot raises a "deprecating hand."
(grimace)- "With a grimace, M. Bouc handed it (the document) back. 'It is not illuminating,' he said."
(masquerading )-"Who was the man or woman masquerading in Wagon Lit uniform?"
(didactically)-M. Bouc continued somewhat didactically."
(unwittingly)- Taken at its simplest, it is a clue which directly incriminates someone whose initial is H, and it was dropped there unwittingly by that person."