One that participates in a marathon, especially a marathon runner.(noun)
American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Use "marathoner" in a sentence
"Davila is best known as a marathoner, and if one (i.e., me) had to predict the 2012 U.S."
"Of course, one does not have to be an actual marathon runner to be a spiritual marathoner."
"Except for the crazy ones, however, no marathoner does this (running, that is)."