(third-person singular simple present decimates, present participle decimating, simple past and past participle decimated)
- (Roman history) To kill one man chosen by lot out of every ten in a legion or other military group.
- To reduce anything by one in ten, or ten percent.
- (historical) To exact a tithe or tax of 10 percent.
- To reduce to one-tenth.
- To severely reduce; to destroy almost completely.
- (computer graphics) To replace a high-resolution model with one of lower resolution but acceptably similar appearance.
The definition reduce by one in ten is occasionally cited as "the correct" definition, with severely reduce considered a misconception, arrived at by reading decimate as to reduce to one-tenth rather than by one-tenth.
The Cambridge Guide to English Usage states that the nonspecific use of this word to mean devastate or severely reduce the numbers of is "nowadays the commonest use of the word in both British and American English, and it’s registered without comment in modern dictionaries." It also advises against using numbers with the term, as "They are redundant where it means 'reduce by one tenth', and where it doesn't they confound the arithmetic."
The 23 occurrences of decimate in the British National Corpus — compare decimates, decimated, and decimating — almost all clearly accord with the nonspecific sense. The only references to the historical sense are two complaints about modern usage and its critics. Neither of these actually uses the term to mean "reduce by one-tenth".
From Latin decimare "to take the tenth (decimus) part of anything", in particular referring to the levying and payment of tithe and also the practice of capital punishment applied to one man at random (by lot) out of every ten in a legion; compare quintate.