strange particle definition by American Heritage Dictionary
nounThe American Heritage® Dictionary of the English Language, 4th edition Copyright © 2010 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
An unstable elementary particle created in high-energy particle collisions having a short life and a strangeness quantum number other than zero.
strange particle - Science Definition
Any of various unstable elementary particles, having a short half-life and a nonzero strangeness quantum number. Sigma and xi baryons, for example, are strange particles.