sodium hydroxiden. A white deliquescent solid, NaOH, that is a strong base used in the manufacture of chemicals and soaps and in petroleum refining. Also called caustic soda, lye.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.sodium hydroxide n (Elements & Compounds) a white deliquescent strongly alkaline solid used in the manufacture of rayon, paper, aluminium, soap, and sodium compounds. Formula: NaOH. Also called: caustic soda See also lye Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014so?dium hydrox?ide n. a white, deliquescent solid, NaOH, used chiefly in the manufacture of other chemicals, rayon, film, soap, as a laboratory reagent, and in medicine as a caustic. Also called caustic soda, soda. [1880?85] Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.sodium hydroxide A strongly alkaline compound, NaOH, used in making chemicals and soaps, in refining petroleum, and as a cleansing agent. In solution, it forms lye.The American Heritage® Student Science Dictionary, Second Edition. Copyright © 2014 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.