beta

1. A mathematical measure of the sensitivity of rates of return on a portfolio or a given stock compared with rates of return on the market as a whole. A high beta (greater than 1.0) indicates moderate or high price volatility. A beta of 1.5 forecasts a 1.5% change in the return on an asset for every 1% change in the return on the market. High-beta stocks are best to own in a strong bull market but are worst to own in a bear market. See also alpha, capital-asset pricing model, portfolio beta.
2. A preliminary version of a software program that may have bugs and isn't ready for final release. Beta versions are distributed to users who understand they are testing a prerelease program.