This is what my Merriam-Webster's 11th Collegiate Dictionary says on the noun:
1 a : an unmarried woman devoted to religion b capitalized : VIRGO
2 a : an absolutely chaste young woman b : an unmarried girl or woman
3 capitalized : VIRGIN MARY
4 a : a person who has not had sexual intercourse b : a person who is inexperienced in a usually specified sphere of activity a virgin in politics
5 : a female animal that has never copulated
This is what my Merriam-Webster's 11th Collegiate Dictionary says on the adjective:
1 : free of impurity or stain : UNSULLIED
2 : CHASTE
3 : characteristic of or befitting a virgin : MODEST
4 : FRESH, UNSPOILED; specifically : not altered by human activity a virgin forest
5 : a (1) : being used or worked for the first time (2) of a metal : produced directly from ore by primary smelting b : INITIAL, FIRST
6 : of a vegetable oil : obtained from the first light pressing and without heating
7 : containing no alcohol a virgin daiquiri
I also looked up my Oxford English Dictionary. The definitions and examples of the word as an adjective and noun are abundant and quite similar to the ones from Merriam-Webster.
Although a virgin is pure, I am not sure exactly what a virgin is pure of. Is the underlying assumption that sexual intercourse is dirty or that sexual misconduct is dirty? Also, when applied to something like a virgin forest, as one of the examples suggests, why would human activity (perhaps walking in the forest) would make the forest fresh or unspoiled by mankind? What if the human being wants to protect the forest because he or she has a green thumb and a passion for nature? Or is that usage referring to the corruption of nature by mankind for self-serving interests (wood, coal, charcoal, luxuries) at the expense of the animals and plants that live there?