noun. A play on the phrase "ladies night" where a group of women go out together for female bonding, usually including drinks. In the case of "lady night" it's when a woman stays home by herself (husband, children, etc. are all out of the house) and drinks wine (or any other alcoholic beverage) while doing something she likes to do alone (read, watch TV, Facebook, knit).
Henry's playing darts tonight and Bijou's staying at a friends so I'm home all alone. I think I'll get some wine and make it lady night!