pump?

My dictionary says pump as a verb is to "operate like a pump". But when on is pumping one's fist, what does one do? I can't picture the action ...

http://www.urbandictionary.com/define.php?term=fist+pump

http://members4.clubphoto.com/_cgi-bin/members/compact_slide_show.pl?album_item_id=29198709

Thank you. The picture really gives me a very clear idea! ^_^

Is 'fist pump' a common word or is it slang and (almost) nobody would understand me, if I used it? Could you give an example sentence? Is it possible to say 'to do a fist pump'?

Thank you.

What I read was something like "I pumped my fist". I think it's pretty common to say so.

What about "pumping" other areas. ;)
Same awkwardness.