a·dul·ter·y (?-d?l?t?-r?, -tr?)n. pl. a·dul·ter·ies Consensual sexual intercourse between a married person and a person other than the spouse.[Middle English, from Old French adultere, from Latin adulterium, from adulter, adulterer; see adulterate.]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.adultery (??d?lt?r?) n, pl -teries (Law) voluntary sexual intercourse between a married man or woman and a partner other than the legal spouse[C15: adulterie, altered (as if directly from Latin adulterium) from C14 avoutrie, via Old French from Latin adulterium, from adulter, back formation from adulter?re. See adulterate]Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014a?dul?ter?y (??d?l t? ri) n., pl. -ter?ies. voluntary sexual intercourse between a married person and someone other than his or her lawful spouse. [1325?75; Middle English a(d)vouterie