Black bottom is a term that refers to the lower part of something that is dark or black in color. There are several synonyms for the word black bottom, such as crux, nadir, base, foundation, bottommost, foot, depth, ground, and bedrock. These words may be used interchangeably depending on the context, but they all convey the idea of the lowest part or foundation of something. Black bottom can also be used to describe a type of dance that originated in the 1920s, which involves fast movements and shaking of the hips. Overall, the synonyms for black bottom vary depending on the usage, but they all refer to the lowermost part of something.