ar·co (är?k?)adv. & adj. Music With a bow. Used chiefly as a direction to indicate the resumption of bowing after a pizzicato passage.[Italian, bow, from Latin arcus.]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.arco (???k??) adva musical direction for instruments of the violin family indicating that the bow should be used (as opposed to plucking)Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014