A 'rahver' (pronounced 'raa-ver') is a tourist at a rave or drum 'n' bass night. Typically found in university towns with large sloane populations (Oxford, Cambridge, parts of London etc.), they will be the ones in the club with loads of luminous paint and accessories like glowsticks, taking more drugs than is necessary and totally not understand what the point of the night is. If asked to name their favourite drum 'n' bass act, they will inevitably say 'Pendulum' and nothing more.
"Went to see Pendulum the other day, but it was rubbish because it was full of rahvers."