Heaps of articles conclude squirt is piss. 'Female ejaculate' is the same. Previous research studied the composition of 'ejaculation' samples and turns out they contained uric acid, urea, creatinine, glucose etc - chemically identical to urine. The only difference is trace amounts of PSA which are released by the Skene gland.
Last year the first study evaluating the origin of the fluid was published. This was a proper, peer reviewed scientific study. Not only the biochemical makeup was tested (and found to be urine), but ultrasounds were used to follow the path of the ejaculate (the 'squirt' flowed from the bladder and expelled through the urethra). The bladder doesn't hold any other liquid, just piss. When sexually aroused, women release PSA via the Skene gland, and traces of this PSA was found in some of the subjects ejaculate samples. This study, and the 2nd most recent publication (2007) both concluded that "The present data based on ultrasonographic bladder monitoring and biochemical analyses indicate that squirting is essentially the involuntary emission of urine during sexual activity, although a marginal contribution of prostatic secretions to the emitted fluid often exists.”
Findings indicated the bladder filled and emptied faster than usual however (resulting in a more diluted urine) and as a result current research is underway to investigate the speed and function of the kidneys in sexual urination.
There is some controversy raised by feminist groups however, who disregard these findings and believe that science doesn't understand true female sexuality yet. Whilst I'd identify as a feminist myself...I gotta say, peer reviewed findings from ultrasounds and biochemical analysis doesn't lie. It comes from where piss comes from, is composed of piss.....is piss. In my mind, that's okay :) were so socialized to think wee is gross but squirt is sexy - people are defensive over this issue. Fucking someone into an orgasm so awesome that they piss themselves is still pretty damn sexy.
Here's the recent study refered to if you'd like a read: http://onlinelibrary.wiley.com/doi/10.1111/jsm.12799/abstract