An unintentional beard started over the 4 day Thanksgiving weekend, where you're too lazy to shave it off monday morning. Usually continues until Christmas or New Year's Day.
Also known as a Holiday Beard
Boss: You look like you haven't shaved in days. That's unprofessional.
Employee: Sir, that's my Thanksgiving beard. It's my way of honoring our forefathers.
Boss: Oh, I didn't realize that. Maybe I'll grow one too.