FB day 

short for a Ferris Bueller day -- in reference to the movie, "Ferris Bueller's Day Off" (1986)

Were you really sick on Friday or just taking an FB day?

FB day by ΔиłĦ☼иצ ߀₡ʞ March 17, 2010

fb-day

The day that your birthday shows up on all of your friends news feeds on Facebook. Also the day after you update your profile picture, information, quotes, likes and interests. The one day of the year that all your facebook friends you never talk to creep on your facebook to see if their life is better then yours.

Justin: You remember Hilary from school?

Brendan: Yeah, its her fb-day today.

Justin: Shes gaining some weight.

Brendan: Her boyfriend has a chin strap.

Justin: Well asleast she listens to the avett brothers

Brendan: I love hipsters

fb-day by PACHYCEPHALOSAURUS March 27, 2011