Fogged in
To have so much fog that traffic (often airplanes) cannot move.The airport was fogged in and we could not leave on our flight .
Foam at the mouth
To be very angry (a sick dog foams at the mouth).My father was foaming at the mouth when I told him that I had damaged his car.
Flying high
To be very happy, to be joyful.My neighbor has been flying high since she won a car.
Fly by the seat of one`s pants
To do a job instinctively rather than by using concrete information.I had to fly by the seat of my pants when my boss left me alone for one week.
Fly-by-night
An unreliable business or person.The new company is a fly-by-night operation.
Flush with (something)
To have lots of something.We were flush with cash so we decided to go on a nice holiday.
Flush with (something)
To be even with something.The two pieces of wood were flush with each other so we glued them together.
Firsthand
Directly.I learned the news from my sister firsthand.
First things first
The most important things must be taken care of first.We did first things first and cleaned the kitchen before cleaning the living room.
First-string
The best group of players on a team.Our team will use their first-string players for the game today.