"Humanoid" is an excellent all-purpose word for describing encountered characters or creatures of not-quite-human appearance or species. It can encompass pretty much anything that stands upright on two legs.* Use the word "humanoid" and it feels like you're giving your players information, but then again the word is so broad that you're practically telling them nothing whatsoever. A humanoid can be a cute and harmless fairy of some sort, or a ravening reptilian monster as tall as a building. Some people might assume a humanoid is something that - if it were a movie - could potentially be played by a person wearing a suit. Somewhat correct as far as it goes, but that leaves out the possibilities of scaling the creature up or down in size dramatically. After all, storm giants are humanoids too.
* Yes, that includes birds.
R2-D2: We search the room.
GM: You find a passage concealed behind a heavy drape.
Luke: A secret door! Let's go!
GM: You find yourself in the wings of the theatre. On stage is a strange green humanoid.
Kermit: Hi ho! Hi Ho! A really great show for you tonight we have!
Angus McGonagle: Are you my father?
Angus McGonagle: My clone father? His name is Mace.
Kermit: Your father I am... not. What are you doing on stage?
Angus McGonagle: I dunno. Nobody ever tells me anything.
Kermit: Get off!
C-3PO: Oh my!
R2-D2: You suggested an improv theatre.
C-3PO: I regret nothing.