An investment strategy or portfolio is considered market-neutral if it seeks to avoid some form of market risk entirely, typically by hedging.
For example, convertible arbitrage attempts to fully hedge fluctuations in the price of the underlying common stock.
A portfolio is truly market-neutral if it exhibits zero correlation with the unwanted source of risk.
[2] A portfolio that appears market-neutral may exhibit unexpected correlations as market conditions change.
Equity-market-neutral is a hedge fund strategy that seeks to exploit investment opportunities unique to some specific group of stocks while maintaining a neutral exposure to broad groups of stocks defined, for example, by sector, industry, market capitalization, country, or region.