Whistle

whistle [countable]

1 a small object that produces a high whistling sound when you blow into it:

The lifeguard blew his whistle.

2 a high sound made by blowing a whistle, by blowing air out through your lips, or when air or steam is forced through a small opening:

Larsson scored just minutes before the final whistle.

low/shrill/high-pitched etc whistle

Sanders gave a low whistle when he saw the contents of the box.

3 a piece of equipment on a train or boat that makes a high noise when air is forced through it

4 the sound of something moving quickly through the air

whistle of

We could hear the whistle of the jets as they passed overhead.

➔ blow the whistle on something

at blow1 (17)

; ➔ clean as a whistle

at clean1 (1), penny whistle, wolf whistle

Definition from the Longman Dictionary of Contemporary English
Advanced Learner's Dictionary.