The bulltards who bought Google's stock at $500, since it was such a great price after falling from $650, have hopefullylearnedsomething now that it's below $400.
The opposite of a docile tard, a bull tard is person who is both retarded* and extremely aggressive. Often possesses "tard strength." This person would rather fight you than talk it out; would rather use violence than intellect; would rather use brute force than finesse.
*Does not necessarily have to be actually retarded...simple dumbasses can also be tards, and by extension, bull tards.