brach·y·ther·a·py (br?k??-th?r??-p?)n. pl. brach·y·ther·a·pies Radiotherapy in which the source of radiation is placed close to the surface of the body or within a body cavity.[brachy- (in reference to the short distances involved) + therapy.]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.brachytherapy (?bræk????r?p?) n (Medicine) a form of radiotherapy in which sealed sources of radioactive material are inserted temporarily into body cavities or directly into tumoursCollins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014