Flourish  

Verb | flur-ish
to prosper, grow, or make fast progress

Foment  

Verb | foh-ment
to stir up

Ferocity  

Noun | fuh-ros-i-tee
viciousness, violence, savage fierceness

Fluctuate  

Verb | fluhk-choo-eyt
to be unstable; to rise and fall

Facilitate  

Verb | fuh-sil-i-teyt
to aid the progress of

Exhilarating  

Adjective | uhg-zi-luh-rayt-uhng
causing strong feelings of excitement and happiness

Exert  

Verb | ig-zurt
to put into use (usually as effort)

Excel  

Verb | ik-sel
to do something extremely well or to be superior in