A multi-polar charge is a high-frequency energy discharge produced inside the nucleogenic cloud being in the Delta Quadrant. They are highly effective against deflector shields, because their polarity rotates so quickly that the shields cannot compensate.
In 2371, after USS Voyager accidentally entered the creature and injured it by collecting omicron particles, the creature generated multi-polar charges in defense. Voyager was able to survive the charges long enough to repair the wound and escape. (VOY: "The Cloud")