Centerline

Noun

1. A line down the center of a road, generally one that divides traffic moving in opposite directions.
2. A line, either demarcated or imagined, representing the precise center (middle) of something (such that what lies on one side of it is precisely equal in size to what lies on the other side); the central axis represented by this line<!--which is quite real albeit invisible, as for example with a center of gravity-->.
3. An imaginary line connecting the center of two fighters' bodies while they face each other.