The act of holding your breath after taking a toke on a spliff then as it becomes more difficult to keep the breath in, breathing in. Aiming to take at least 3 breaths before it becomes unbearable and you have to let it out.
Helps if you are standing to allow your lungs full capacity but be sure you have a friend who can catch you when you forget your legs are there!
Dude: Hey man, you know when you hold your breath after a toke, try to breath in when it gets hard to hold it!
Man: *tries* Woooah! Dude, I'm sparrowing!