A very agreeable person. A Yes Man is a person who always agrees with a person further up in the power hierarchy then them. A person who tells people what they want to hear. Usually seen as weak willed people who agrees with their superior out of fear of retribution for disagreement. While logically yes men are not seen as good to have around, obviously you want advisors who are going to give you a thoughtful response and try to give you the best advice they can. But we are human and not always logical creatures. Sometime we only want to have our opinions confirmed by somebody else, even if it isn't the best thing, and we can sometimes become quite irate when given opposing opinions.