Plain English Meaning
Fly the assigned heading until you are a certain distance from a named DME station, then start the next part of the procedure.
Full Definition
A VD leg is an ARINC 424 path-and-terminator leg type in which the aircraft flies a specified magnetic heading until it reaches a defined DME slant-range distance from a referenced DME station, at which point the leg terminates and the next leg begins. The 'V' identifies the path as a heading (not a track), and the 'D' identifies the terminator as a DME distance.
Context Anchor
Seen in instrument-procedure design and flight-management-system database coding, especially in discussions of .