noun plural
: beds of coal with the associated rocks varying in thickness from a few feet to several thousand feet and consisting of shales, sandstones, limestones, and conglomerates with interstratified beds of coal and occasionally of iron ore
noun plural
: beds of coal with the associated rocks varying in thickness from a few feet to several thousand feet and consisting of shales, sandstones, limestones, and conglomerates with interstratified beds of coal and occasionally of iron ore
Webster's New International English Dictionary. Новый международный словарь английского языка Webster. 2012