Reference
How sensitive a stock's returns are to the overall market's — calculated as the covariance of the stock's returns with a benchmark (PSEye's reconstructed composite index), divided by the benchmark's variance. A beta above 1 means the stock tends to swing more than the market in the same direction; below 1, less; negative is rare but means it tends to move opposite the market.
See every term in the full PSE investing glossary.