Mä·lar·en (m??lär??n) A lake of southeast Sweden. Stockholm is located on both sides of the channel that connects the lake with the Baltic Sea.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.Mälaren (?melaren) n (Placename) Lake Mälaren a lake in S Sweden, extending 121 km (75 miles) west from Stockholm, where it joins with an inlet of the Baltic Sea (the Saltsjön). Area: 1140 sq km (440 sq miles). Also called: Mälar Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014