look up because something may hit you.

Usage notes: often shouted as a warning:

Heads up! Watch out for the baseball!

• credit someone with
• credit someone with something
• the letter of the law
• the lie of the land
• the life of the party
• the light at the end of the tunnel
• the lights are on but nobody's home.
• the lights are on but no-one's home.
• the lions' den
• the lion's share
• the long and the short of it
• the long arm of the law
• the love of life
• the love of your life
• the lowest common denominator
• the lowest of the low
• the low man on the totem pole
• the luck of the draw
• the lull before the storm
• the main drag
• them and us
• the man in the street
• the man of dreams
• the man of the moment
• the man of your dreams