Feeding Frenzy: An aggressive attack on someone by a group.
Field Day: An enjoyable day or circumstance.
Finding Your Feet: To become more comfortable in whatever you are doing.
Finger lickin' good: A very tasty food or meal.
Fixed In Your Ways: Not willing or wanting to change from your normal way of doing something.
Flash In The Pan: Something that shows potential or looks promising in the beginning but fails to deliver anything in the end.
Flea Market: A swap meet. A place where people gather to buy and sell inexpensive goods.
Flesh and Blood: This idiom can mean living material of which people are made of, or it can refer to someone's family.
Flip The Bird: To raise your middle finger at someone.
Foam at the Mouth: To be enraged and show it.
Fools' Gold: Iron pyrites, a worthless rock that resembles real gold.
From Rags To Riches: To go from being very poor to being very wealthy.
Fuddy-duddy: An old-fashioned and foolish type of person.
Full Monty: This idiom can mean either, "the whole thing" or "completely nude".
Funny Farm: A mental institutional facility.