To grow larger; to dilate or extend the exterior surface or dimensions, by matter added within, or by expansion of the inclosed substance; as, the legs swell in dropsy; a bruised part swells; a bladder swells by inflation.(verb)
source: webster1913
To increase the size, bulk, or dimensions of; to cause to rise, dilate, or increase; as, rains and dissolving snow swell the rivers in spring; immigration swells the population.(verb)