a ball of clear crystal, glass, or the like, used in crystal gazing.
a method or means of predicting the future.
Origin of crystal ball
First recorded in 1850–55
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
the glass globe used in crystal gazing
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 means of predicting the future, as in So what does your crystal ball say about the coming election? The term is a figurative use of the crystal or glass ball used by fortune-tellers. [c. 1900]
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.