Facebook Display of Affection. As opposed to a PDA (Public Dispay of Affection), an FDA is an over the top way of letting everybody know you love and lust for your significant other through Facebook.
I can't believe my freakin' dad posted an FDA today. Check this shit out -"I'm just thinking about my beautiful wife who is as hot today as she was 25 years ago when I married her. I can't wait to get you in the sack tonight, baby!!!"