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1.
An action where you put your two arms out to your side and curve your arms and scoop your hands inwards as your flapping your arms up and down.
Band Member 1 "What is he doing?"
Band Member 2 "He's trying to pump up the crowd for our next song American Idiot"
by inspire62 September 17, 2010
 
2.
the act of influencing a crowd to show more attention and excitement towards a lack luster band or song. Arm movements towards the sky, a "c'mon" or eyebrows and head raised are typical ways for a band to improve the fan experience.
The crowd was enjoying the show in their own way until the band needed to pump up the crowd where everybody was asked to raise their arms to please the band's request.

Thankfully, Auberbach decided to pump up the crowd. Then it was a party.

Yeah, I never seen Thom Yorke try to pump the crowd before. I really wish he could interact with his fans more often.
by drfunkenstein September 29, 2014