Forgot to mention my age – 48.
According to my ID card, me.
A, 32.
From another planet
19
B, 40. I would only think of definition A if given a context (a conversation, an adjective, something).
From another planet…like Mexico.
45
B, 14
Beings from another world.
25.
I read a LOT of sci-fi.
I’d go by content, but in the absence of a clue, I’d understand it to mean extraterrestrial rather than extra-American. 
Of course, I’ve been a SF reader for over 45 years now (thanks to my aunt who got me started on it at age 9).
55
OT bad joke: The unidentified government agents who are seeking out ET and his young friends in the movie? They’re the I.N.S. – not having his green card, ET is obviously an illegal alien! 
Another vote for “without context, they’re from other planets.”
I’m 28.
And geeky enough that I am beyond thrilled that I finally got my paws on the B5 fifth season set. That means I have the WHOLE SHOW. And I’ve hooked my boyfriend on it, and it’s so much fun watching him watch it…
Yep. From another planet. Like my brother.
Without any context, and alien is a being from another planet. I’m 25.
When I saw the thread title, I assumed you were talking about the second type. However, that might have been a consequence of your using the phrase what are they?, as opposed to who are they? or what are they like?. Still, you can mark my answer in the “B” column.
Thank you for all your replies.
I asked this question because I had recently been reminded of certain instances where actors were asked to asked to play “Aliens” but somehow got the idea they were supposed to play immigrants.
I thought it wierd because I myself had always thought of some kind of extra-terrestial being when I heard the term “Alien” and I wondered if It was a generational thing(I’m 22 and a Sci-fi fan) but after seeing the replies from this thread, now it appears I was wrong.
You may be right about the generation thing, but at age 22 you are at least 2nd or maybe 3rd generation (I am 47 myself).
On the other hand, my grandfather was always interested in TV and newspaper accounts of purported UFO sitings … :dubious:
A. Secret
B. 36
oops I fucked that up.
A. Depends on the context. - usually little green man.
For a second there I was wondering if you worked for the Government agency that does not exist.
- A) person from another planet
- 27
I can’t say that I’ve ever heard a reference to aliens that meant otherwise without being preceeded by “illegal” or “legal.”