to make a high or musical sound by blowing air out through your lips:
high sound[intransitive and transitive]C
Adam whistled happily on his way to work.
I heard this song on the radio and I've been whistling it all day.
He whistled a tune as he strolled down the corridor.
whistle to somebody (=whistle to get someone's attention)
Dad whistled to us to come home for dinner.
whistle at somebody (=whistle to let someone know that you think they are attractive)
Men are always whistling at Heidi on the street.
to make a high sound by blowing into a whistle:
use a whistle[intransitive]CDS
The referee whistled and the game began.
to move quickly, making a whistling sound:
go/move fast[intransitive always + adverb/preposition]C
Bullets and shells were whistling overhead.
They listened to the wind whistling through the trees.
if a steam train or kettle whistles, it makes a high sound when air or steam is forced through a small hole
if a bird whistles, it makes a high musical sound
to be trying to show that you are brave when you are afraid, or that you know about something when you do not:
Does he know what he's talking about or is he just whistling in the dark?
7 British English spoken
used to tell someone that there is no chance of them getting what they have asked for