look up any word, like cleveland steamer:
 
2.
Newfie slang, expressing disbelief or amazement.
" I want a gold toilet"
"yes b'y"

or

" My cat just had puppies"
" yes b'y"
by Emily April 25, 2005
 
1.
An expession Newfoundlanders use which could show the emotions of amazement, disbelief, agreement, etc. and also can be very sarcastic.
"I got so loaded last night I fucked my cat"
"Yes b'y!"
by shanty for the arethusa March 04, 2006
 
3.
Newfy slang to express affirmation or assent or to mark the addition of something emphasizing and amplifying a previous statement
Would you fuck her?
Yes by!
by The Mac February 09, 2012