Decimate is defined as to destroy or kill a large part of something.(verb)
An example of decimate is for a natural disaster to kill a large portion of a population.
See decimate in Webster's New World College Dictionary
See decimate in American Heritage Dictionary 4
transitive verb dec·i·mat·ed, dec·i·mat·ing, dec·i·mates
Origin: Latin decimāre, decimāt-, to punish every tenth person
Origin: , from decimus, tenth
Origin: , from decem, ten; see dekm̥ in Indo-European roots.
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