verb (used with object), un·der·ran, un·der·run, un·der·run·ning.
- to run, pass, or go under.
- Nautical. to pass beneath (a stretched rope, net, etc.) in a boat or the like for the purpose of inspection or repairs.
- something that runs or passes underneath, as a current.
- an instance of costing or spending less than estimated.
- a production run of a manufactured or printed item below the quantity ordered.