A wild man (or wildman) or wild woman was an individual who lived in the wild or acted uncivilized.
According to Human mythology, Enkidu was "a wildman from the forest." (TNG: "Darmok")
After James T. Kirk was split into two following a 2266 transporter accident, and the "evil" Kirk entered sickbay, Spock later reported to the "good" Kirk that after his entrance into sickbay, "our good doctor said that you were acting like a wild man, demanded brandy." (TOS: "The Enemy Within")
Believing Sakonna would change her mind about dancing after drinking some wine, Quark opined in 2370, " Somewhere inside that cool, controlled exterior of yours, there's a wild woman screaming to get out." (DS9: "The Maquis, Part I")