The rate below which a load costs you money to haul.
Your cost per mile, plus whatever margin you need to still be here next year. Below it you are paying to work.
Breakeven is per-lane, not one number for the whole business. A lane with a reliable backhaul carries a lower breakeven than one that sends you home empty.
Related
Inteleri works out what a load actually pays you once things like this land. See how it works.