According to Wikipedia, countersignalling is "the behavior where agents with the highest level of a given property
invest less into proving it than individuals with a medium level of the
same property". In other words, it means "showing off by refusing to show off" - and thereby differentiating yourself from those who have to show off, in order to distinguish themselves from those who have nothing to show off. A good example is seen in the behaviour of old-money aristocrats who downplay their wealth and disdain to spend money on frivolities, distinguishing themselves from parvenus who have to buy all sorts of status symbols in order to distinguish themselves from the working class.
