
“prediscursive” just means “before being discussed.” basically, a lot of people assume that sex is “real” and exists prior to being socially constructed. the point that sex is observed and defined through social construction. for ex, many people use chromosomes to define “sex” but they were only discovered in the last century, so the way that “sex” is defined has shifted over time.
also worth noting that prior to the 1960s “sex” encompassed all aspects of what we think of as “sex” and “gender” (physical, social, psychological, aesthetic, religious, etc). the distinction was introduced in a medical setting to talk about *children* (primarily intersex but also some trans) who deviated from their assignment. highly highly recommend “histories of the transgender child” by gill-peterson to learn more.