I like the use of the word tacky here. So-called might work better for you than fraudulent .
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sam1947But, if you are speaking of the case of one man, on one trip that he has engineered just so he can cheat on his wife, I would refer to it as the "so called" business trip, if the cheating wasn't taking place in the context of a real business trip where the cheating was just thrown in for good measure (which happens sometimes), and I would ref
VorparI wouldn't call lying to one's wife tacky, unless the situation were a bit different. Perhaps taking the wife with him to New York as a second honeymoon to gain the opportunity to cheat would be tacky.