What is outperform?

Some articles on outperform:

Index Fund - Disadvantages - Cannot Outperform The Target Index
... By design, an index fund seeks to match rather than outperform the target index ... Therefore, a good index fund with low tracking error will not generally outperform the index, but rather produces a rate of return similar to the index minus fund costs ...
Reliability of Election Stock Markets
... (2008) also report evidence that election stock markets outperform polls for longer time periods before the election date ... Erikson and Wlezien (2008) challenge the view that election stock markets outperform polls ... using statistical techniques, they find that poll-based forecasts outperform vote-share market prices ...