gid·dy·up(gĭd′ē-ŭp′) also gid·dy·ap (-ăp′, -ŭp′) or gid·dap (gĭ-dăp′, -dŭp′)
Used to command a horse to go ahead or go at a faster pace.
[Alteration of get up.]
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.
an exclamation used to make a horse go faster
[C20: colloquial form of get up]
Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014
Command to a horse to start or to move faster.
1001 Words and Phrases You Never Knew You Didn’t Know by W.R. Runyan Copyright © 2011 by W.R. Runyan