Derived from the expression "get a room." When couples constantly leave romantic, mushy or suggestive messages on each other's Facebook wall for everyone else to see, someone else may tell them to "get an inbox already" and carry on in private.
Sadie: I love you SO FUCKING MUCH ahhhhhhh Im gonna die from how much I love you <3 <3 <3
When you have no messages in your email inbox. Such a goal is often elusive, because the more email you clear out and reply to, the more new messages come in.
I reached my goal of inbox zero by Friday afternoon, but Monday morning I had 42 new messages.