A general state of chaos or disarray. Similar to clusterfuck.
The ancient British originally used the word 'fuckslug' in situations where the word 'fuckton' was too hyperbolic and generally just over the top. With a decline in the use of slugs as a mass unit, the seventeenth century saw a reversal of the word into 'slugfuck', and a further evolution of its meaning to the current usage.
Rob: Wait a second - is it ton, tonne, or tun? God, this whole system is a complete slugfuck.
Steve: I know. Fucking brits.