Undemonstrative means not given to showing feeling openly. An undemonstrative man.
It says nothing about what is felt, only about what is shown. An undemonstrative family can be as close as any other and looks colder to outsiders.
1adjectiveundemonstrativeNot given to showing feeling openly.
“He was undemonstrative to the point that people thought him cold.”
undemonstrative is a quality.
From un- + demonstrative.
Etymology from Wiktionary, CC BY-SA