Underweight refers to two different financial situations: (1) a portfolio that holds a smaller amount of a security when compared with a benchmark and (2) an analyst's opinion regarding the future performance of a security.In the first case, an investor may be underweight in XYZ stock because they believe it is overvalued relative to the rest of the market. This means they are holding less XYZ than what would be considered normal or "average." The second case is more common among professional analysts who make recommendations to their clients. They may rate XYZ as "underweight" meaning they think it will perform below average or expectations in comparison to its peers.