ABYB
A.B.Y.B stands for an Anti Banter Young Bastard/Bitch. This can be interpretated as a young person who is very anti-social and does not join in conversations or general fun or as someone who is...frigid. the latter usage is generally considered to be offensive.
"that boy is such an ABYB..."
"Hey, don't be an ABYB man join in the fun!"
"Hey, don't be an ABYB man join in the fun!"