A 'Boy-off' is a person who ditches you. This person will 'boy' you off often in favour of doing something else.
"Oh Ollie is such a boy-off"
"Holly just boyed me off for Jenny"
"Just boy your work off an come see me instead?"
to be rude or to ignore or to walk away from someone.
oi! he just walked away from me! smack that boy-off!