telltale
n.— «They’ve got a “tell-tale” tracking needle on the tachometer. Shows you the highest RPM a driver just reached on the track.» —“Studdard’s Ambition Burns On: At Age 51, SCCA Driver Wants to Try NASCAR” by Bill Robinson Atlanta Journal-Constitution (Ga.) Oct. 15, 1989. (source: Double-Tongued Dictionary)
Further reading
Imagine telling someone how to get to your home, but without using the name of your street, or any other street within ten miles. Could you do it? We take street names for granted, but these words are useful for far more, like applying for a job or...
