jumpy rpms!

i noticed recently that i'm having a problem with my car. first of all, it's an automatic. it usually happens in 1st and 2and 2nd gear, but sometimes i've noticed it in 3rd. i'll be driving along normally, not really accelerating, then all of the sudden my rpms will jump up by 2k and i'll have to let my foot off the gas completely so i dont redline. any suggestions as to what this could be?
 
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