A current below the surface of water, sometimes flowing in a contrary direction to that on the surface.

Hence, figuratively, a tendency of feeling, opinion, or the like, in a direction contrary to what is publicly shown; an unseen influence or tendency; as, a strong undercurrent of sentiment in favor of a prisoner.

Running beneath the surface; hidden.

Undercurrent is a 1963 album by the jazz pianist Bill Evans, and the jazz guitarist Jim Hall. They would collaborate again in 1966 for the follow-up album Intermodulation.

Undercurrent is a 1946 film drama directed by Vincente Minnelli.

subdued emotional quality underlying an utterance; implicit meaning