A man interested in snaring a wealthy woman. The phrase was first heard after World War I, when it was applied to musicians who performed in supper clubs and kept an eye out for susceptible women of means. As the century progressed, a man didn't have to be a musician; any well-dressed predatory male earned that phrase. Some say “lizard” referred to reptile shoes that were popular footwear; other say the word applies to the men's low-life character. “Lounge lizard” is the male equivalent of “gold digger.”