Definition 1: Something or someone that at first, shows great promise and then turns out to be total shit.
Definition 2: Once a great Metal band from Nashville but hasn't really been shit since the second singer left. Main reason the band hasn't gone anywhere? The guitar player thinks he is gods gift to music. He is full of himself and holds the members to high standards that he himself is not subject to. They used to be a really good metal band. But they keep chasing the latest fads and have not maintained any kind of consistency with their sound or lineup since the first singer left. Such a shame and waste of many opportunities.

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.