What does the british dialect lorry mean in English dialect?

"Lorry" is not actually a British dialect word. It's the standard British English term for what Americans call a "semi-trailer truck" or simply "truck".

The word "lorry" is derived from the older word "lorry", which was a type of heavy wagon, and it is still the most common term for large commercial vehicles in the UK.

So, when someone in Britain says "lorry", they are simply referring to a large vehicle used for transporting goods.