In the old days, 'mistress of the night' or 'lady of the night' meant that a women was a suductress, harlet, or whore. It also is a statement that applies to certain pop culture madams, such as Elvira. "Unpleasant dreams..."
by Jennisis January 28, 2016
The evening before Valentine's Day when you are supposed to take out your mistress. Whereas on Valentine's Day you take out your wife or girlfriend.
I told my wife I was going to play basketball with the guys on mistress night, but I really took Susan to dinner.
by Patrick Ransom February 13, 2010