A stock in a portfolio that one holds for the long-term. For example, if one buys a blue-chip stock and never sells it, this is considered a core holding in one's portfolio. Stocks that investors include in their core holdings are usually relatively low-risk and have a history of a solid (if not very large) return.
An investment expected to be part of a portfolio over a long period of time. For example, an investor may consider shares of Intel, Procter & Gamble, and General Electric as core holdings to be supplemented by other investments with short- and intermediate-term holding periods.