Aloof
Etymology
Originally a nautical term: a-loof meant "to the luff," toward the windward side, from the command to steer a ship’s head into the wind and away from a hazardous shore. "To keep aloof" was to keep clear, at a safe distance. That maritime "hold off, keep away" hardened into the social sense of keeping oneself coolly apart.
adjective · /uh-LOOF/
Cool and distant, keeping oneself emotionally or socially apart from others.
What it names
The deliberate reserve of someone who is present in the room but pointedly holds back from the warmth around them.
Example
The visiting author remained aloof at the reception, nodding politely but joining no one’s conversation.
Related idea
Detached suggests calm impartiality or lack of involvement; aloof adds a note of chilliness, a sense of holding others deliberately at arm’s length.