point source

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A source, especially of pollution or radiation, occupying a very small area and having a concentrated output.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun sciences 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.
• noun mathematics the abstract concept of a singularity emitting a flux or flow. A source with infinitesimal dimensions in space.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a concentrated source (especially of radiation or pollution) that is spatially constricted