ok its pretty simple:
a prude-slut is a girl who goes out with alot of guys, but doesn't ever do anything with them, even just kissing.

The safeguarding of Earth and other worlds from biological cross-contamination (i.e. billionaires with too much time on their hands).

Also known as “planetary protection.” Planetary protection / quarantine “reflects both the unknown nature of the space environment and the desire of the scientific community to preserve the pristine nature of celestial bodies until they can be studied in detail.”

There are two types of interplanetary contamination. Forward contamination is the transfer of viable organisms from Earth to another celestial body. Back contamination is the transfer of extraterrestrial organisms, if such exist, back to the Earth's biosphere.

A girl who acts like a prude, but at the end of the night is definitely going home with somebody.

A person who has 'slutty' sexual desires and would love to fuck lots of people but doesn't act on this as they are actually a prude (for various reasons-morale society/family/shame/stigma/religion/ frigid-slut etc.) so won't, hence the term prude-slut.

the biggest oxy-moron in the world... i dont know what it means

someone who is a slut when drunk and prude when sober.

while sounding like an oxymoron, this word describes a girl or boy who gets with a lot of guys but does not go far with any of them.