a telltale patch of oil on the water marked where the boat went down.
Examples of telltale
telltale
This telltale flicker is easy to spot even from a small, ground-based telescope.
From the time.com
A telltale sign is an arsenal of smaller steam pitchers, instead of one big one.
From the nytimes.com
Sodium is a telltale sign of cool, neutral gas in the vicinity of the explosion.
From the sciencedaily.com
They waited for the telltale nibbles that make anglers jump up and set the hook.
From the washingtontimes.com
The next morning, he'd be grumpy and puffy-eyed, telltale signs he hadn't slept.
From the timesunion.com
Instead, Reagan reversed course without any telltale dimming of his jolly smile.
From the tennessean.com
One of the telltale signs of a CO2 leakage was a stinging sensation in the nose.
From the newscientist.com
On my fourth cast I felt the telltale tick of a fish inhaling the plastic worm.
From the dailyherald.com
Instead, the Bank of England tracks data on internet searches for telltale terms.
From the economist.com
More examples
Revealing: disclosing unintentionally; "a telling smile"; "a telltale panel of lights"; "a telltale patch of oil on the water marked where the boat went down"
Tattletale: someone who gossips indiscreetly
Telltale were a group of six musicians who regularly appeared on the first series of the British TV series Rainbow in 1973.
One who divulges private information with intent to hurt others; Tattletale; squealer; Something that serves to reveal something else; A length of yarn or ribbon attached to a sail or shroud etc to indicate the direction of the flow of the air relative to the boat; revealing something not ...
(Telltales) Short pieces of yarn attached to the shrouds, or the sails. At the shrouds they indicate the direction of the wind (the apparent wind), and at the sails they help to check the air flow over the sail, so that proper trimming is easier.
(TELLTALES) These are strips of wool or nylon which are sewn or fastened on the Jib Luffs and Leech of Mainsail. Know the function of Telltales in our Five Sailing Essentials section.
(TELLTALES) Any device that serves as a warning. Specifically the row of strips hanging down a short distance in front of a tunnel or low bridge to inform trainmen who are riding car tops that they'd better duck
(Telltales) Short lengths of wool indicating wind direction.
(tell-tales) small lengths of wood sewn through a sail near the luff and leech to allow the air flow over the sail to be checked.