What is a "hashed transaction" in SQL Server Replication terminology? sys.dm_repl_tranhash contains information about the hashing of transactions, but I have difficulties understanding the terminology. What is a "hashed transaction"?
In reality, this DMV (Dynamic Management View) won't be very helpful for a DBA or Developer and is geared to SQL server Product Support and Product Group. You can ignore this DMV.

Hash tables work well when there are a small number of items that fit into a bucket and this is an example of a DMV that support might use to check certain internal structures without the need of obtaining a dump or using a debugger.

There are various other DMVs that fall into this category and you'll find they either aren't documented at all, or there is only extremely light and vague documentation. This falls into that category.