I couldn't find a definition for "bull nose pliers". I've had a look at the results in Google Images and it looks to me that "bull-nose pliers" could be a synonym for "combination pliers" and "Lineman's pliers", but I'm no expert. Wikipedia, however, lists only Lineman's, linesman's (US English), linesman pliers (Canadian English), combination pliers and side-cutting plier for the same type of pliers. Bull nose pliers don't appear on their site at all as a term, and it's hard for me to make out any particular characteristics of this tool to set it apart.
Perhaps the term is regional. I'm in the midwest in the United States, and I have heard the term "bull-nosed pliers," but I've never heard of "combination pliers" or "linesman's pliers" before.
It's not a term I've heard in a while, but as far as I know, bull-nosed pliers are a stubbier version of needle-nosed pliers.
So here's some "regular" pliers – note the adjustable joint and how the jaws sort of make a circle:
Then here's some bull-nosed pliers – note the lack of adjustable joint and how the jaws touch from top to bottom:
Bull-nosed pliers are contrasted against needle-nosed pliers, which are more long and pointy, and the jaws of which also touch from top to bottom:
The bottom part of the jaws on bull-nosed and needle-nosed pliers also often comes to a somewhat sharp point on the inside to allow for cutting wires and whatnot. (This is shown in the pictures above, though you may not be able to tell that's what's going on if you haven't seen such a pair of pliers in person before.) But I'm not sure that's a mandatory feature for a pair of pliers to qualify as needle-nosed or bull-nosed. The more distinguishing features are the length of the jaws and the lack of adjustable joint.