Grasswhistle 

a term used used for when a vegan moans while getting head.

i heard them damn vegans blowing the grasswhistle

Grasswhistle by bootyisvegan May 6, 2023

Grass Whistle 

An offensive manuever done by bending over and placing your head between your legs. Then take your middle finger and put it right in front of your ass, and fart. Your finger will resemble a blade of grass as it blows through the wind.

He really must have been pissed, because he totally gave that guy the grass whistle.

Grass Whistle by th3_duk3 September 8, 2009