decimate [LME] When Roman legions mutinied, they would be decimated—one in every ten men would be selected by lot and executed. In its first recorded use in English, in the late 16th century, decimate refers to this practice, but by the early 17th century people were using it of other acts of killing, destroying, or removing one in ten. They then lost sight of the military context, and by the mid 17th century any severe loss or destruction could be described as decimation.