What makes it prayer?

What makes a prayer a prayer? I wrestled with this while trying to decide whether to participate in the Atheist Experiment project. Justin Brierley read a comment from an Unbelievable listener indicating that an atheist's prayer is a misnomer, because one requirement of prayer is belief.
Clearly Tim Mawson, whose paper stimulated this project, disagrees.

I liken this project to sitting in a broadcast studio with a microphone that may or may not be live. And which may or may not be connected to a broadcast tower. And the tower may or may not be broadcasting on the right frequency. And there may not be radios out there to receive the signal.  And there may not be anyone with those radios on.  And there may not be an Anyone at all.

Come to think of it, I think we've just created celestial SETI.