Flop
To crash, lurk or chillax.

Flow Flat
Wave conditions that exist during a flat spell. It implies more than just that it's flat, but that it has been flat and may remain flat for extended periods of time. The word was coined by Don The Klank Klankhauf circa 1969 during a Sunday afternoon cocktail party during a flat spell in which he complained, Craaaap!, it's so flat it's fo-flat!.

Fluff
Spray dispersing off the lip of a breaking wave.

Flutes
Modification to a swallow tail board design where small channels are incorporated into the underside of the tail from about three inches up from the boards trailing edge.

Foam
1) The liquid polyethylene material used to mold surfboard blanks, which hardens or cures into a soft but firm foam, and is then shaped by hand. 2) Also the white water of a breaking wave and/or the bubbles left over from a breaking wave.

Foam Ball
To inadvertently or purposefully turn a hollow section of a wave into foam by shoulder hopping or other means - preventing a potential tube ride. Example: "I was about to get shacked when that kook tried to catch my wave and foamballed me."

Foamer
A person who rides the foam whitewater of the wave.

Foil
1) The rate of change of thickness from nose to tail of a surfboard. 2) The rate of change of thickness of a surfboard fin from its front to its back edge.

Footwells
The pressure dings that occur on a surfboard deck in the feet placement areas. Caused by the downward pressure of the riders weight being applied to the surface of the board during high-energy, torque generating turns that compresses the foam under the glass layer.

Forehand
(see frontside)

Forerunners
1.5 times the swell period to be exact.

Forward Vee
(see reverse vee)

Foul
Something that's really bad, rank, nasty.

Four One One/411
Adopted from the former Bell System Information Number. Applied today in a broader sense to indicate information.

Franklins
Specific application of Dead Presidents, describing US Currency. A One Hundred Dollar Bill displays the portrait of Benjamin Franklin.

Freddie
Similar to Barney or Kook, but more reckless and dangerous to other surfers. Is derived from the character, "Freddie" in the movie Nightmare on Elm Street. May also be called Fredrico or Fredrica (for women Freddies).

Freight Train
An adjective applied to barrel describe an extremely fast and usually sketchy wave setup that causes it to suddenly jack and pitch as it forms a hollow tube.

Freeboarding
Generally refers to the act of riding a surfboard behind a boat, similar to water skiing. Tow-in surfing's humble origins.

Frequency Downshifting
Occurrence when the wave period within a fetch increases. Therefore, a decrease in frequency is an increase in the period or length of time between successive wave crests.