tach·y·on
(tăk′ē-ŏn′)n. A hypothetical subatomic particle that always travels faster than the speed of light.
tach′y·on′ic adj.
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
tachyon
(ˈtækɪˌɒn) n (Nuclear Physics) physics a hypothetical elementary particle capable of travelling faster than the velocity of light
[C20: from tachy- + -on]
Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014
tach•y•on
(ˈtæk iˌɒn)
n. a hypothetical subatomic particle that travels faster than the speed of light.
[1967; < Greek tachý(s) swift]
Random House Kernerman Webster's College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.