a·ce·tyl·cho·li·nes·ter·ase (?-s?t?l-k??l?-n?s?t?-r?s?, -r?z?)n. An enzyme in the blood and in certain tissues that catalyzes the hydrolysis of acetylcholine.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.acetylcholinesterase (??si?ta?l?k??li?n??st?r?e?z; ?æs?ta?l-) n (Biochemistry) an enzyme in nerve cells that is responsible for the destruction of acetylcholine and thus for switching off excitation of the nerveCollins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014a?ce?tyl?cho?lin?es?ter?ase (??sit l?ko? l??n?s t??re?s, -?re?z, ??s?t-, ?æs ? tl-) n. an enzyme that counteracts the effects of acetylcholine by hydrolyzing it to choline and acetate. [1945?50] Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.