Idiom: To pile up
Mother: Can you please clean your room? Your dirty clothes are starting to pile up. Pretty soon you will have a mountain of dirty clothes.
Daughter: Ok Mom! Don't worry. I promise I'll put all my dirty clothes in the laundry basket before I go to bed tonight.
Tom: Wow! Today was so busy at work. I was sick for three days so I couldn't come in to work. Now my work has piled up for three days. I checked my email and I had like 50 messages in my inbox.
Joe: Sounds like you will be busy this week. Good luck catching up on all those emails.
Meaning: the idiom "to pile up" is used when the amount of something increases to a relatively large amount. It is usually used for things like work, clothes, books, and other random things.
This idiom can be found in the LSI textbook Speaking Transitions which is used to teach Level 4 Speaking/Listening classes at LSI schools. For more information please visit www.languagesystems.com