When your fucking a female with a very loose vagina, and you start eating her out. Her vagina is so loose that it all falls out and slaps you right in the face.

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.

The female genetalia - specifically the outer labia
See: Tuna Taco, Beef Curtains, Sticky Mittens, Spam Castanets, Fuzzy Lap Flounder

When you stretch your partners vagina lips out so far that she slaps you with her pussy lips