Crossing Over is an origin trait in Destiny 2 that can appear on 10 weapons. There is also an enhanced version with a stronger effect.
What Crossing Over does
This weapon has increased range and handling for the top half of the magazine, while rounds from the bottom half of the magazine deal increased damage.
Enhanced version
This weapon has significantly increased range and handling for the top half of the magazine, while rounds from the bottom half of the magazine deal significantly increased damage.