Sentence examples for not cool from inspiring English sources

The phrase "not cool" is correct and can be used in written English.
It is commonly used in informal language and expressions to convey that something is not acceptable, desirable, or impressive. Example: - "Your behavior last night was not cool. You should apologize to your friend." - "I can't believe you forgot my birthday. That's really not cool." - "It's not cool to make fun of someone's appearance." - "His lack of respect for others is definitely not cool."