The original entry for this read simply “the wrecking ball”, a name for a freakish anatomical manifestation that once afflicted a friend of a friend and has fascinated many FT writers since they first heard about it. It describes a partial erection of the male member such that while the glans is engorged, the shaft remains flaccid. Hence, as you now realise, the name.
The wrecking ball could not apparently be summoned on demand (just as well really) and it can be filed alongside other minor quirks like tingly nipples, webbed toes and so on. Of course as inexplicable phenomena these are failures – if medical science has not yet investigated the genetic causes of webbed toes it’s most likely because it can’t be arsed to, rather than because it faces the limits of puny human understanding. But as ‘strange phenomena’ – well, the mix of horror and queasy imaginings the ‘wrecking ball’ elicits among male pubgoers puts it firmly (well, semi-firmly) in this category.