A date a homosexual person takes to a (work, family) holiday party (eg work xmas party) to disguise the fact of their homosexuality.
May not be their regular Beard
due to the overbooking experienced during the holiday season.
"Hey dude, who's that chick your brother's with? I thought he was gay?"
"Oh, he hasn't come out to our parents yet, so that's just his Holiday Beard."