any of certain aquatic plants belonging to the genus Nymphoides, of the gentian family, especially N. aquatica, having floating, more or less heart-shaped leaves and a cluster of small, white, five-petaled flowers.
a related plant, Nymphoides cordata, of North America, having a cluster of white flowers and round or somewhat oval leaves that are purple beneath.
Origin of floating heart
An Americanism dating back to 1855–60
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
British Dictionary definitions for floating heart
any perennial aquatic freshwater plant of the genus Nymphoides, esp N. lacunosum, having floating heart-shaped leaves: family Menyanthaceae
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