a trough filled with liquid, especially water, for collecting gases in bell jars or the like by displacement.
Origin of pneumatic trough
First recorded in 1820–30
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
British Dictionary definitions for pneumatic trough
chem a shallow dishlike vessel filled with a liquid, usually water, and used in collecting gases by displacement of liquid from a filled jar held with its open end under the surface of the liquid
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