False Favorite
Horse that is a race favorite despite being outclassed by other competition in the field. Also called an underlay.  

Farrier
Horseshoer, blacksmith. Also called a "plater."  

Fast (track)
Footing that is dry, even and resilient.  

Fee
1) Amount paid to a driver for in a race. 2) The cost of nominating, entering or starting a horse in a stakes race.  

Field
The horses in a race.  

Field Horse (or mutuel field)
Two or more starters running as a single betting unit (entry), when there are more starters in a race than positions on the totalizator board.  

Filly
Female horse four-years-old or younger.  

Fire
A burst of acceleration by a horse in a race. The horse did (didn't) fire when asked.  

Firm (turf)
A condition of a turf course corresponding to fast on a dirt track.  

Flatten Out
A very tired horse that slows considerably, dropping its head on a straight line with its body. Some horses, however, like to run with their heads lowered.