Definitions

1. noun

A being or entity that is partially of another world or of non-human origin, especially one that is not fully accepted or understood.

“The sci-fi movie depicted a semialien species that struggled to adapt to human society.”

2. adjective

Partially of another world or of non-human origin; not fully human or of this world.

“The semialien child grew up with an unusual ability to communicate with animals.”