n common thorny tropical American tree having terminal racemes of yellow flowers followed by sickle-shaped or circinate edible pods and yielding good timber and a yellow dye and mucilaginous gum
n the central part of a car wheel (or fan or propeller etc) through which the shaft or axle passes
n a center of activity or interest or commerce or transportation; a focal point around which events revolve
the playground is the hub of parental supervision the airport is the economic hub of the area
n United States astronomer who discovered that (as the universe expands) the speed with which nebulae recede increases with their distance from the observer (1889-1953)
n (cosmology) the ratio of the speed of recession of a galaxy (due to the expansion of the universe) to its distance from the observer; the Hubble constant is not actually a constant, but is regarded as measuring the expansion rate today