People from outerspace. Generally peace loving and wise, they've come to Earth because we've got velcro and they love that shit

Briefly, "the realization that each random passerby is living a life as vivid and complex as your own." Originally from the Dictionary of Obscure Sorrows, which has a lot more beautiful neologism definitions like this you might enjoy.

Far out dudes that love some good kush. Can be often seen flyin around in their saucerz stoned af looking for some dank weed that humans crop. Their language consists of 'Ayy' and "lmao' said in varying lengths and tones.

1. In terrestrial terms, those who come from another country, a.k.a. immigrant.

2. Usually refers to any being that isn't from the planet earth, a.k.a. extraterrestrials (E.T.)

Something that stupid people say don't exist

An excellent science fiction movie series. Features a race of insect-like aliens called Xenomorphs, which have acidic blood and a collective mentality. They lay eggs like normal insects, but the larvae can only mature into adults by leaping onto a host organism's face and injecting themselves dow into the digestive tract. The adults burrow themselves out of the host, killing it in the process.
Basically, if you have an alien Xenomorph on your planet, your species is doomed.

1. A person from a foreign country
2. An extra-terrestrial being.