Mike, its a less than flattering term associated with drift boat fishing. When a group of angler are anchored on one or more fish, an approaching boat steers clear to not disturb their fish. As the second boat is about to over take the anchored boat, They sometimes lift anchor and drop down river. Or the passing boat will anchor directly below first boat. Thus "Low Holing" becomes the oar powered equilivant of road rage.
Thus the phase. "That SOB in the red clacka low holed me the whole way from Balls Eddy to Buckingham."
Anchored boats are generally given the right of way and boats underway pass on one side or another depending on which side the guys are fishing on.
Equally frustrating is the high hole method.
In fishing, just like other aspects of life, respect and courtesy can be damn hard to come by sometimes.