Woof woof is very similar to grrr as in it means whoever is on the receiving end of it is looking mighty fine. You are also very likely to get laid a lot if people say woof woof to you. It's probably best used towards men however as you dont want the woman to think you mean she is dog which is completely different

The sound a dog makes.

An expression of negativity. An exclaimation of disapproval of the current situation at hand.

when a flacid man stands up and violently moves his hips back and forth to make his dick and balls slap his stomach and ass.

An act of sexual intercourse, that resembles that of dogs do it; also known as doggy.

a scary looking guy. referred to as a "woof woof".

When things aren’t the way they should be. Not normal.