High crime. It's "high crime". I mean, if you're wanting to be all technical and stuff, you should probably look up the actual term used. Here...I'll help. Then we can re-visit your question.
a crime of infamous nature contrary to public morality but not technically constituting a felony; specifically : an offense that the U.S. Senate deems to constitute an adequate ground for removal of the president, vice president, or any civil officer as a person unfit to… See the full definition
www.merriam-webster.com
a crime of infamous nature contrary to public morality but not technically constituting a felony
specifically : an offense that the U.S. Senate deems to constitute an adequate ground for removal of the president, vice president, or any civil officer as a person unfit to hold public office and deserving of impeachment
So, if it's not a felony and it's not a misdemeanor, it defaults to the actual definition used for it by the people who wrote it. Which is
offenses as varied as misappropriating government funds, appointing unfit subordinates, not prosecuting cases, promoting themselves ahead of more deserving candidates, threatening a grand jury, disobeying an order from Congress.
None of those things is an actual crime. However, they can be considered "high crimes".