telltale
Concise Oxford English Dictionary © 2008 Oxford University Press:
telltale/ˈtelteɪl/
▶adjective revealing or betraying something. ▶noun
- 1 Brit. a person who reports others' wrongdoings or reveals their secrets.
- 2 a device or object that automatically gives a visual indication of the state or presence of something.
'telltale' also found in these Oxford entries:

