PSA is what Southwest Airlines used to be called (Pacific Southwest Airlines). Although prostate glands don’t fly, it is also an abbreviation for prostate specific antigen, which is made by the prostate gland and helps liquefy semen after it’s been ejaculated. The liquefying action of PSA is what makes male ejaculate drip out of a woman’s vagina after intercourse. PSA tends to be elevated in men who have prostate cancer. PSA can be checked via a routine blood test, but that is never definitive of cancer by itself. PSA is present in very small amounts in breast milk and amniotic fluid.