slang for a gun.heard mostly in the hbo series "The Wire".

What you do when a girl as hot as fuck walks by.

First entry is completely correct.

But to add some interesting info... The term 'whistle' is used a multitude of times throughout HBO's, 'The Wire'. Although it is never distinguished or addressed directly, it becomes apparent that the term 'whistle' really refers to ONLY a pistol, a semi-matic handgun.

David Simon's bestseller book and basically the father/catalyst of The Wire is 'Homicide'. Again the term 'whistle' is NOT explicitly defined) (Wether its only a pistol, or maybe a type of Mac/Tec or a shotgun) However the book does make it clear that 'whistle' is a term used in Baltimore. This isn't explained out right, but through stories, recorded conversations with citizens and the times when slang was recorded throughout the book, it becomes abundantly clear that the use of the term is authentic, meaning 'whistle' is actively used there.

Another name for a quickly made Crack pipe consisting of a can bent around the leg and cigarette ashes.

Whis·tle (wĭs′əl, hwĭs′-)
n.

The unit of measurement for kratom dosage. A "whistle of kratom" or simply a "whistle" is a moderate dose of kratom that is equivalent to approximately 2.5-3 grams of powdered kratom. The slang is mainly used in the Midwest and West of the United States. The term has been said to originate from a technique of powdered kratom ingestion which aims at reducing the tasting of the powder. A whistle is a dose that makes for a successful ingestion of the drug using this technique without feeling the strong taste or smell of the kratom. Such an administration is "clean as a whistle", hence the name.

Suit. From Cockney rhyming slang: whistle and flute

Slang term for cell phone.