Loud and clear
Clear and distinct.I could hear the announcement loud and clear.
Lost on (someone)
To be wasted or have no effect on someone.My attempt at telling a joke was lost on my former girlfriend.
Lost in thought
To be busy thinking.I was lost in thought when my friend phoned last night.
A lost cause
A hopeless matter.Trying to change the work habits of our secretary is a lost cause. She will never change.
Lost and gone forever
Permanently lost.My father's pocket knife is lost and gone forever and we will never see it again.
Lost-and-found
A place that handles lost items that other people find.I went to the lost-and-found department at the train station to look for my umbrella.
Lose weight
To decrease one's weight.I want to lose weight so I have stopped eating sweets.
Lose track of (someone or something)
To lose contact with someone or something.I have lost track of my friends from high school.
Lose touch with (someone)
To fail to keep in contact or communication with someone.I lost touch with the people who I worked with at my summer job.
Lose sleep over (someone or something)
To worry about someone or something so that you cannot sleep.I have been losing sleep over my recent problems at work.