For me scud running is when an attempt is made to fly VFR in minimal VFR conditions which would preclude the 2000 foot cloud base
unless you were flying the Alps!
Pace
My previous point exactly - one man's scud running is not another mans.
Where do you draw the line? Are you happy with 1,000 feet between base and terrain, 500 feet, I know you get the picture. That is the problem with these generilsations, what you or I think of as scud running might be very different from another pilots. Even the aircraft might be a factor. Scud running at 200 knots is one skill set, different and more challenging than at 80 knots.
Short of fog it is surprising what conditions you might enjoy a scud run along coastal beaches.