to destroy a great number or proportion of: The population was decimated by a plague.
to select by lot and kill every tenth person of.
Obsolete. to take a tenth of or from.
Origin of decimate
1590–1600; < Latindecimātus, past participle of decimāre “to punish every tenth man chosen by lot,” verbal derivative of decimus “tenth,” derivative of decemten; see -ate1
Related formsdec·i·ma·tion, noundec·i·ma·tor, nounCan be confuseddecimaldecimatedecimatedestroy (see usage note at the current entry)
The earliest English sense of decimate is “to select by lot and execute every tenth soldier of (a unit).” The extended sense “destroy a great number or proportion of” developed in the 19th century: Cholera decimated the urban population. Because the etymological sense of one-tenth remains to some extent, decimate is not ordinarily used with exact fractions or percentages: Drought has destroyed (not decimated ) nearly 80 percent of the cattle.
c.1600, in reference to the practice of punishing mutinous military units by capital execution of one in every 10, by lot; from Latin decimatus, past participle of decimare (see decimation). Killing one in ten, chosen by lots, from a rebellious city or a mutinous army was a common punishment in classical times. The word has been used (incorrectly, to the irritation of pedants) since 1660s for "destroy a large portion of." Related: Decimated; decimating.