point source

Short definition from Wiktionary

Noun

1. 1
   a source of pollution, radiation, waves, fluid or other substance that has one specific location (and negligible physical extent, distinguishing a point source from other source geometries). In simulations they can often be approximated using mathematical point sources.
2. 2
   the abstract concept of a singularity emitting a flux or flow. A source with infinitesimal dimensions in space.