1. Threatening to do something to you, but is not really willing to do it.
2. Acting all tough, intimidating, and agressive, but is too cowardly and chicken and/or also not strong enough to be willing to even throw one single punch at you.
This idiom is so called, because these kinds of people are likened to dogs who keep barking at you to try to make you afraid, but are actually not going to bite you.
Tyrone: "You gotta be kidding me, bitch! I am all jonesing for this shit right here like a kid in a candy store when all of a sudden, some rhesus monkey from down the block tries to run up my quality time!"
Jamal: "Shove a sock in it, fool! This be my quality time and I am the one who's gonna chuck it in her! Get anywhere near her and my crack rock, and you'll be lying bernie in a pool of your own blood and cellulite!"
Tyrone: "*laughs hysterically* You!? Some half pint threatening to blast a gat on me?! Where's yo gat anyway? *laughs some more* All bark and no bite! *puts on spiked brass knuckles*"
Jamal: "You one stupid ass nigga, you know! Glad I got my spazz by my side! *Jamal quickly pulls out his shotgun from underneath his trenchcoat(where Tyrone doesn't notice it) and points it at Tyrone* Now who's all bark and no bite now, BITCH!"
Tyrone: *soils his pants and runs home crying*
Jamal: *takes the crack rock*
Jamal: (to the girl) Alright baby, now let's go back to my place and hit the sack. I've got everything you want and everything you need.
Mark H. UrbanDictionary disciple since February 2004.