Pronunciation: (ri-tûrn'flOO'), [key]
a fire-tube boiler having flues that collect the combustion gases at the end of the boiler opposite the fire door and pass them through the boiler to an uptake above the fire door. Also called re•turn'-tu'bu•lar boil"er Pronunciation: (ri-tûrn'tOO'byu-lur, -tyOO'-). [key]
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.