1. the compactness of the constituent elements of something, reflecting its degree of impenetrability.

2. a measure of the amount of physical space per individual. High density can produce crowding, the feeling of having insufficient space. Interior indices of density (e.g., people per room) are consistently related to negative psychological consequences, whereas external indices (e.g., people per square mile) are not. See also social density; spatial density. —dense adj.