a vessel similar to a catamaran but having three separate hulls.
Origin of trimaran
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
a vessel, usually of shallow draught, with two hulls flanking the main hull
Word Origin for trimaran
C20: from tri- + (cata) maran
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012