The word "coterminous" has related words "contiguous", "coextant", "conterminous" and "continental". When referring to the "Lower 48" United States (excluding Alaska and Hawaii), the words have slightly different meaning, although they get used interchangeably often and the world does not fall apart. Contiguous means that each of the 48 states border at least one other state via a land or river border, or a water border if it's in a sheltered bay like the Chesapeake Bay. Coterminous means that the 48 states are enclosed within an encompassing boundary. Coextant means that the 48 states together compose the "Lower 48" states, in the sense that the pieces of a puzzle together compose the entire puzzle. Conterminous means that two states share a common border. For example, Arizona and New Mexico are conterminous, but Arizona and Maryland are not. Continental means that the states lie on the same continent. Thus, Alaska is also "in" the Continental United States. The assemblage of the 48 states often gets referred to as the coterminous United States, or the contiguous United States. I think the first one is more appropriate, in that the 48 states are all contained within one external boundary. Contiguous is not incorrect, but not as strong as coterminous. I've never been a fan of "Lower 48", since it seems we need to emphasize it excludes Alaska, as if that's not clear by context. Should we then call Alaska the "Upper 1 State"? This is my take on the matter. You may feel differently.