The turntable definition almostkindasorta works as an onomatopoetic interpretaion of a DJ's scratching, but any DJ simply repeating a "Waka" sound over and over, without throwing in at least one, say, "Whee" isn't worth his headphones. The other def...the one about P.E.? That one just makes no sense.
The male genital used as a rope. When a person is in need of a rope, but no nylon, hemp or polypropylene is available, a waka waka rope is often convenient. Depending on the tensile threshold of the waka waka rope, it can replace other rope in all situations.
Yo girl, come jiggle my waka waka rope and lasso me some naughty naughty.