To be in a delicate
situation; to be on the edge of danger or ruin.
1) Ever since
I smashed their car, I've been walking on eggshells with my parents.
2) We're walking on
eggshells with our landlord -- she told us that if we have one more loud
party, she's going to kick us out of our apartment.
An 'eggshell' is the
thin, white outer coating of an egg. The shell is very thin and breaks
easily. So if you are 'walking on eggshells' you are in a situation
where you could break something ( or get in trouble or ruin everything )