such as
I wouldn't say that was the archetypical BSO. Indeed, it looks suspiciously like the decomposing remains of an actual bicycle.
BSOs are the ones purchased from the likes of supermarkets, Sports Direct and Halfrauds
[1], and are the
transportation sports equipment equivalent of those almost-but-not-quite-copyright-infringing children's toys you find in markets and pound shops: The idea being that to the untrained eye they're indistinguishable from the real thing.
Standard features include 'suspension' with ineffective damping; low-end grip shifters that broke ages ago so the chain is permanently in small:small; an unhooked rear V-brake in order to accommodate the severely-out-of-true wheel; forks may optionally be fitted backwards, and lighting - if present - tends towards the anaemic glow-worm end of the spectrum, often with disregard for the usual conventions on lighting colours for road use.
While their half-life is fairly short, they have wheels and are faster than walking, which makes them the transportation method of choice for the bus-route-impaired budget-conscious Brit.
[1] Who have muddied the waters in recent years by adding proper bicycles to their range, too.