1. The degree of mutual agreement among a series of individual measurements, values, or results; often, but not necessarily, expressed by the standard deviation.
2. With respect to a set of independent devices of the same design, the ability of these devices to produce the same value or result, given the same input conditions and operating in the same environment.
3. With respect to a single device, put into operation repeatedly without adjustments, the ability to produce the same value or result, given the same input conditions and operating in the same environment. Synonym (for defs. 1, 2, and 3) reproducibility.
4. In computer science, a measure of the ability to distinguish between nearly equal values.
5. The degree of discrimination with which a quantity is stated; for example, a three-digit numeral to the base 10 discriminates among 1000 possibilities.
Source: from Federal Standard 1037C and from MIL-STD-188
6. In information retrieval it forms a pair with recall and is a measure of the number of relevant documents in the set of all documents returned by a search.
7. In the game of Contract Bridge, one of the bidding systems used by expert players.