The tip of the iceberg is the small visible part of a much bigger problem. That is only the tip of the iceberg.
About a tenth of real ice shows above water, which is exactly the proportion the phrase implies. It is used to warn that what has come out so far is the least of it.
1nounthe tip of the icebergThe small visible part of a much bigger problem.
“The two cases reported are the tip of the iceberg.”
the tip of the iceberg is a phrase.
Practised in Idioms