The #1 place I hear people use this unusual term is standards people talking about standards stuff. It's not an intuitive term, but what it means is quite a useful and short way to describe a certain situation.
Bikeshedding means talking/arguing about something easy/trivial rather than the bigger/harder issue at hand.
a committee whose job is to approve plans for a nuclear power plant may spend the majority of its time on relatively unimportant but easy-to-grasp issues, such as what materials to use for the staff bikeshed, while neglecting the design of the power plant itself, which is far more important but also far more difficult to criticize constructively.
It's an accusation of wasting time.
Technical disputes over minor, marginal issues conducted while more serious ones are being overlooked. The implied image is of people arguing over what color to paint the bicycle shed while the house is not finished.
So next time someone wants to have five meetings about selector methodology you are going to use before you actually build the dang website, you can scream bikeshedding!