The term "width dimension" refers to the measurement of how wide or broad something is. It helps describe the horizontal extent or size of an object or space. Full definition
Similar to its width, its track width dimensions were also modified. (thetorquereport.com)
This would desirable if you want do sumo deadlifts, sumo rack pulls or sumo squats inside the rack, and if your sumo stance width is actually greater than 42» (the internal width dimension of both the T - 3 and X-3). (kingofthegym.com)
Please note your cover designer will need to know the paper type for the spine width dimensions since white and cream paper has different thicknesses. (bbebooksthailand.com)