noun Physics, Optics.
a source of radiation sufficiently distant compared to its length and width that it can be considered as a point.
Origin of point source
First recorded in 1900–05
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
optics a source of light or other radiation that can be considered to have negligible dimensions
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
A source, especially of pollution or radiation, occupying a very small area and having a concentrated output.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.