poin·set·ti·a (poin-s?t??-?, -s?t??)n. A shrub (Euphorbia pulcherrima) native to Mexico that has a cluster of small yellow flowers surrounded by showy, usually scarlet petal-like bracts.[New Latin, after Joel Roberts Poinsett (1779-1851), American diplomat who sent samples of the plant to the United States while in Mexico.]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.poinsettia (p??n?s?t??) n (Plants) a euphorbiaceous shrub, Euphorbia (or Poinsettia) pulcherrima, of Mexico and Central America, widely cultivated for its showy scarlet bracts, which resemble petals[C19: New Latin, from the name of J. P. Poinsett (1799?1851), US Minister to Mexico, who introduced it to the US]Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014poin?set?ti?a (p??n?s?t i ?, -?s?t ?) n., pl. -ti?as. a plant, Euphorbia pulcherrima, of the spurge family, native to Mexico and Central America, having variously lobed leaves and brilliant scarlet, pink, or white petallike bracts. [