To warn someone that they are about to be investigated
“The company was tipped off about the tax audit so the accountants had time to prepare for it.”
Tipping point
The point at which mass consumption occurs
“The tipping point for portable digital music players was 2004.”
Tip-toe around
To be very careful not to anger or offend someone
“We have been tip-toeing around for weeks because our boss is so stressed out.”
On the tip of one’s tongue
To not be able to recall on demand though one knows the answer
“What is her name? Oh, it’s on the tip of my tongue!”
Tip of the iceberg
A small noticeable piece of a much larger problem
“The fake designer handbags sold at the street market were just the tip of the iceberg; the police later found several warehouses full of fake designer goods.”