The term I learned was "vinculum." The same term (and symbol) has other meanings in mathematics as well; as far as I know there isn't a specific term that ONLY means the bar used to indicate a repeating decimal.
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The bar is only used for repeating decimals. If it is repeating, you can use it.
A bar.
_ 5.921
.2333 with the bar over the 333
2.16 with a bar on top of the 16