Temperature:
* Cold: This is the most general synonym.
* Cool: A milder form of cold.
* Freezing: Very cold.
* Frigid: Extremely cold.
* Icy: Feeling like ice.
* Brrr: A word expressing a feeling of coldness.
Atmosphere:
* Unfriendly: If referring to a chilly atmosphere.
* Hostile: A stronger version of unfriendly.
* Awkward: If referring to an uncomfortable social situation.
* Tensed: Suggesting a feeling of nervousness or tension.
Other:
* Cool: Can also refer to a person who is aloof or distant.
* Reserved: Someone who is reluctant to express their feelings.
* Unenthusiastic: Lacking interest or excitement.
To choose the best synonym, consider the context and the specific meaning you want to convey.