Dude
General reference to a male surfer. It's use has evolved into a word used for just about anyone or anything.

Dudette
General reference to a male surfer. It's use has evolved into a word used for just about anyone or anything.

Dumping
Used to describe waves that are very hollow and hard-breaking.

Dune
A big peaking wave. Usually a longer period swell that builds more energy as it approaches a shallow area and jacks.

Dunzo 
Meaning done, finished.

Duration
In wave forecasting, the length of time the wind blows in the same direction over the swell generating area, or the fetch. Duration is one of the three key elements in the fundamental wave generation formula-along with wind velocity and fetch length-used to determine wave heights and wave periods in a storm or wave generating area.

Dynocabbie
Coined for a parents vehicle that takes the kids to the beach for a surf.