Marvin the Martian, for example

adjective

1. Belonging or relating to another person, place, or thing strange

   "an alien environment"

2. Relating, belonging, or owing allegiance to another country or government foreign

   "alien residents"

3. Exotic

   "alien plants"

4. Coming from another world extraterrestrial

   "alien beings"

5. Differing in nature or character typically to the point of incompatibility

   "ideas alien to democracy"

noun

1. A person who is not of a particular group or place

   "aliens seeking asylum in the U.S."

2. A foreign-born resident who has not been naturalized and is still a subject or citizen of a foreign country
3. Extraterrestrial

   "a movie about an invasion of Earth by monstrous aliens"

4. Exotic

   "Russian thistle, kudzu, and other aliens"

verb

1. Alienate, estrange
2. To transfer the title of (property)

adjective

1. Opposed or hostile toward aliens

   "anti-alien legislation"

noun

1. A foreign person who lives in a country without having official permission to live there

noun

1. A person who is born in another country and is not considered a permanent resident of the U.S.

noun

1. A foreign person who is living in a country without having official permission to live there

   "trying to do something about the problem of illegal aliens"