If you say that someone is stand-offish, you mean that they behave in a formal and rather unfriendly way.

What does it mean for a person to be standoffish?

adjective. somewhat aloof or reserved; cold and unfriendly.

What does it mean if someone is aloof?

: removed or distant either physically or emotionally an aloof, unfriendly manner He stood aloof from worldly success.— John Buchan.