1whis·tle 
/ˈwɪsəl/ noun
plural whis·tles /ˈwɪsəl/ noun [count] 1 a : a small device that makes a very high and loud sound when a person blows air through it
▪ The policeman blew his whistle.
b : a device through which air or steam is forced to produce a very high and loud sound
▪ a factory whistle ▪ We could hear the train's whistle. — see also bells and whistles 2 : a high and loud sound made by forcing air through your lips or teeth
▪ He gave a whistle [=he whistled] to catch my attention. — see also wolf whistle 3 : a sound made by blowing
▪ We could hear the low whistle of the wind through the trees. ▪ the whistle of the tea kettle
▪ The policeman blew his whistle.
b : a device through which air or steam is forced to produce a very high and loud sound
▪ a factory whistle ▪ We could hear the train's whistle. — see also bells and whistles
▪ He gave a whistle [=he whistled] to catch my attention. — see also wolf whistle
▪ We could hear the low whistle of the wind through the trees. ▪ the whistle of the tea kettle
blow the whistle
: to tell police, reporters, etc., about something (such as a crime) that has been kept secret — usually + on ▪ He blew the whistle on the company's illegal hiring practices. — see also whistle-blower
clean as a whistle
informal : very clean
▪ We scrubbed the old boat until it was (as) clean as a whistle.
▪ We scrubbed the old boat until it was (as) clean as a whistle.
wet your whistle
US, informal : to have a drink
▪ Would you like to wet your whistle? [=would you like a drink?]
▪ Would you like to wet your whistle? [=would you like a drink?]
