Key limen. See Mexican lime.[After the Florida Keys (because it was formerly widely cultivated in Florida).]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.Key? lime? n. a yellow lime with a bitter rather than sour taste. [after the Florida Keys] Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.