This is the 8724th most frequent Portuguese word.
alheia
"Alheia" means "unrelated" or "foreign" (not belonging or connected to someone).
In this sentence, 'alheia' means 'others' or 'belonging to someone else', referring to matters outside of one's own business.
Ela sempre vive preocupada com a vida alheia.
She always lives worried about others' lives.
Here, 'alheia' modifies 'propriedade', indicating that the property belongs to someone else.
Não toque em propriedade alheia sem permissão.
Do not touch someone else's property without permission.
In this usage, 'alheio' refers to being detached or disconnected from something, in this case, the surroundings.