Tartuffe is a French word. As both an adjective and noun, it means hypocrite. As for the proper noun usage of the word, Tartuffe refers to the character (by the same name) in Moliere's play Tartuffe. When translated, the title of the play (in English) is The Imposter (or L'Imposter).
The character of Tartuffe proves to be both an imposter and a hypocrite. He takes advantage of Orgon (a man who he has met at church and invited him to live at his home). Orgon, impressed by Tartuffe's religious nature, wishes him to marry his daughter (Mariane). Orgon is so taken with Tartuffe that he denies his own son in order to allow Tartuffe the rights to his (Orgon's) wealth.
Tartuffe proves to be both a hypocrite and impostor. He is not the pious man Orgon believes him to be. Instead, he is a man whose past is riddled with crimes and deceit.