Someone who is weak, useless, and all round pathetic
Matt is such a weak dog!
What a weak dog!
Somebody who commits low acts of doggatory towards their mates on regualr occasions, and show no signs of every stoping.
1) Julie Gillard is a weak dog for what she did to K-Rudd
2) Ben is a weak dog for not telling James that the teachers where at the door before he called Ben a weak dog cunt