FOAB doesn't necessarily mean that the speaker is busy, there are several situations in which it can be used.

Scenario 1 - Using it to respond to a stupid suggestion with indignity

Person 1: Hey you wanna go to the pictures?
Person 2: FOAB

Scenario 2 - Using it to dismiss somebody with discontent

Person 1: Hey guys, what you up to?
Group: FOAB

Scenario 3 - Reflecting your
by FiveCard April 10, 2015
Get the mug
Get a FOAB mug for your Facebook friend Yasemin.