Dictionary:

countercurrent

  (koun'tər-kûr'ənt, -kŭr'-)

A current that flows in an opposite direction to the flow of another current.

Flowing in an opposite direction.

• c. exchanger — a countercurrent system in which transport between the inflow and the outflow is passive.
• c. multiplier — a mechanism that enables a membrane to absorb much more solute than water so that the residual fluid has a lower osmotic pressure. The classical example of this phenomenon is the loop of Henle in the kidney. Called also countercurrent multiplier mechanism or system.

The noun has one meaning:

Meaning #1: actions counter to the main group activity