This study shows that a supersonic moon shadow of a total solar eclipse can steepen the ionospheric total electron content (TEC) wave on August 21, 2017. A data-adaptive method named Hilbert-Huang transform is employed to examine the nonlinear and non-stationary evolution of the waves. The results show that the TEC wave behaves as a traveling ionospheric disturbance before the totality appearance, turns later into steepening, and breaks eventually. A TEC wave with a period of ∼40 min and wavelength of ∼1,000 km propagates mainly in an east-southward direction before the totality appearance. The wave amplitude and scales, respectively, increases and reduce by near ∼50% as the moon shadow approaches the western coast of the continental United States. The short-period TEC waves (period ∼2 min) reveal that the wave may break eventually when the wave gets steeper. The steepness of the TEC wave is reconstructed according to the constructive interference.