1. extremely good.

Their chocolate cake is just out of this world!

2. extremely expensive.

The price of gasoline is out of this world right now.

• feel your oats
• feel your way
• feet of clay
• feet on the ground
• femme fatale
• fender bender
• fend for
• fend for yourself
• fend off
• fend off someone
• fend off something
• ferret out
• ferret out something
• fever pitch
• few and far between
• few fries short of a Happy Meal
• fiddle away
• fiddle away something
• fiddle while Rome burns
• fiddle with
• fiddle with something
• fifth wheel
• fifty-fifty
• fifty-fifty chance
• fight a losing battle