Writing HBD on someone's Facebook wall instead of happy birthday translates to, "I like you, just not enough to type two whole words."
@Rollinintheseat, October, 2015
"HBD" is what you write when:
Your fingers are lazy.
Your care factor is zero, or thereabouts.
You've had a creative brain fart.
Adam Bub, mamamia.com.au, May, 2017
#HBD to America’s 3rd president, Thomas Jefferson!
@HouseGOP, April 2018