undercurrent

A current of water which flows under the surface, and often in a different direction from surface currents.

For that an undercurrent (which ſome have beleived,) in the ſtraights-mouth, will not ſolve this difficulty, unleſs occaſioned by a vaſt Gulf that muſt be placed ſomewhere in the Atlantic near the Mouth of the ſtraight, which though overflown and hidden by that mighty ſea, yet may poſſibly abſorb the deeper waters, and ſo cauſe a contrary undercurrent.

[W]e have a surface current of saltish water from the poles towards the equator, and an undercurrent of water, saltier and heavier, from the equator to the poles. This undercurrent supplies in a great measure the salt which the upper current, freighted with fresh water from the clouds and rivers, carries back.

A tendency of feeling or opinion that is concealed rather than exposed.

The meeting was pervaded with an undercurrent of dread, as the managers tried not to admit that firings were looming.

All the while there was a busy undercurrent in her, like the thought of a man who keeps up a dialogue while he is considering how he can slip away.

To flow under some surface.

The latter are stoically steady, impervious to the nervousness that still continues to undercurrent the Stock Exchange generally, despite an all-round rally.

Her lips hardly moving, every feature steady, she undercurrented my narrative with ejaculations in French, Russian, Italian.