A person who gets more irratable or sad in the Winter because they don't like snow or cold.
Guy 1: I don't get why my girlfriends been sadder than normal. She's been pregnant for a month now and she was so happy at first, but ever since winter just started, she's been sadder.
Guy 2: Aww, I don't know...Maybe she just has a case of WINTER DEPRESSION. Obviously, she can't be PMSing
Guy 1: Ya you're probably right about having Winter Depression.
Guy 2: I mean have you been in any recent fights with her?
Guy 1: Nothing recent.
Guy 2: Then you've got nothing to worry about