abbreviation for (Commerce) adjustable rate mortgage Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014 arm1 (ɑrm) n. 1. a. the upper limb of the human body. b. the ...