I. tell ‧ tale 1 /ˈtelteɪl/ BrE AmE adjective
telltale signs/marks etc signs etc that clearly show something has happened or exists, often something that is a secret:
They examined the child carefully, looking for telltale signs of abuse.
II. telltale 2 BrE AmE noun [countable] British English
a child who tells adults about other children’s secrets or bad behaviour – used by children to show disapproval SYN tattletale American English