RPE, I believe, stands for Rating of Perceived Exertion. It basically a subjective guide to exercise intensity. Check out this link: http://www.sportfit.com/sportfitglossary/RPE.html
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TRX-Hip press...I'll assume that you have the TRX suspension training system and are going through that program? If not, that workout is designed specifically for use with the TRX suspension trainer.
I google searched and found the TRX Hip Press exercise here along with a video demonstration: