Yes and no.
That is, you can put your procedure in master and call it sp_somename. Then you can invoke it as
The procedure will then execute in the context of the database you specified.
However, this is not supported and it could break, for instance if Microsoft ships a system procedure with name you use. Or it just stops working.
Note here that the procedure name must start with sp_.
Erland Sommarskog, SQL Server MVP, www.sommarskog.se