Wiktionary
capital market line
n. (context finance English) A line representing the relationship between expected return and standard deviation.
Wikipedia
Capital market line
Capital market line (CML) is the tangent line drawn from the point of the risk-free asset to the feasible region for risky assets. The tangency point M represents the market portfolio, so named since all rational investors (minimum variance criterion) should hold their risky assets in the same proportions as their weights in the market portfolio.