The American Heritage® Dictionary of the English Language, 4th Edition
n. Any of several plants of the genus Dahlia native to the mountains of Mexico, Central America, and Colombia, having tuberous roots and showy, rayed, variously colored flower heads.
n. Any plant of the genus Dahlia, tuberous perennial flowering plants native to Mexico.
the GNU version of the Collaborative International Dictionary of English
n. A genus of plants native to Mexico and Central America, of the order Compositæ; also, any plant or flower of the genus. The numerous varieties of cultivated dahlias bear conspicuous flowers which differ in color.
The Century Dictionary and Cyclopedia
n. A genus of plants, natural order Compositæ, of which several species are known, all natives of Mexico and Central America.
n. [lowercase] A plant of the genus Dahlia.
n. [lowercase] In dyeing, a violet coal-tar color consisting of the ethyl and methyl derivatives of rosaniline.
WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
n. any of several plants of or developed from the species Dahlia pinnata having tuberous roots and showy rayed variously colored flower heads; native to the mountains of Mexico and Central America and Colombia
Word Usage
"The term "dahlia" is used for the first time in 1791, when Cavanilles publishes Icones et Descriptiones Plantarum."