This is a type of Globe Base commonly refereed to Bayonet Cap.

Bayonet bases or caps are often abbreviated to BC, often with a number after.
The number refers to the diameter of the base (e.g., BC22 is a 22 mm diameter bayonet cap lamp).
BC15, a 15 mm base, can also be referred to as SBC standing for small bayonet cap

While there are many sizes of BC bases available the two 2 most commonly found in light fittings are B22 (BC) and B15 (SBC).