fusible resistor, yes they are made in this style, primarily for fusing against a direct short across mains I think, while not fusing for transient high voltages. The fusing characteristic would be determined by the power rating I expect, but I'm not familiar. Compare a non-fusible of the same specs could be significantly overloaded and get hot enough to ignite things (you can easily overload a 5w wire wound resistor to such a point that the wire is visible glowing red hot). In other words, fusible resistors are supposed to fail in a safe manner, standard ones however may fail in undesirable ways.