Bull
Black's Law Dictionary · Henry Campbell Black, M.A. · 1910
Black's Law Dictionary
In ecclesiastical law
An instrument granted by the pope of Rome, and sealed with a seal of lead, containing some decree, commandment or other public act, emanating from the pontiff. Bull, in this sense, corresponds with edict or letters patent from other governments.
Cowell; 4 Bl. Comm. 110; 4 Steph. Comm. 177, 179.
This is also a cant term of the Stock Exchange, meaning one who speculates for a rise in the market.