tyre wall defect

That’s clearly damaged, you can see the impact points on the rim and the weak point on the tyre.

The types of thing you’re probably referring to re. DVSA are likely heavy manufacturing joins which can look quite dramatic but are not defects.

To answer the original question it’s a bulge caused by the sidewall being too weak to properly contain the pressure

Sorry Dynamo, I missed out the question, I use "Has a bulge, caused by separation or partial failure of its structure
5.2.3 (d) (ii)" too

I’ve always believed a bulge to require some form of pressure (not specifically in relation to tyres) whereas a lump would be there irrespective.

I vaguely remember VOSA saying something like...

A lump is an deformed area of the tyre that has no structure to it, or something along those lines? I've always asked myself that question about which is which?

Just use what you want jock it's the same thing really like you say jock