fallow
(adj) ground that is plowed but left idle to replenish
fathom
(n/v) to grasp, understand, comprehend
fecund
(adj) fruitful in offspring, vegetation; intellectually productive or inventive
fetid
(adj) having an offensive smell; foul-smelling
frugal
(adj) not wasteful, careful with money
gambol
(v) to run and skip playfully; to frolic
garish
(adj) to be overly; ostentatious; colorful to the point of bad taste
garrulous
(adj) excessively or tiresomely talkative; loquacious
giddy
(adj) to be lighthearted and happy, to be dizzy
gregarious
(adj) one who enjoys being in crowds and socializing; sociable