Alien adjectives are listed in this post. Each word below can often be found in front of the noun alien in the same sentence. This reference page can help answer the question what are some adjectives commonly used for describing ALIEN.
illegal, little
nonresident, resident
such, undesirable
undocumented
Hope this word list had the adjective used with alien you were looking for. Additional describing words / adjectives that describe / adjectives of various nouns can be found in the other pages on this website.
Wierd
Out of control
Rude
Slimy
Ugly