What do the HT* wait types mean? (HTREPARTITION, HTDELETE, ...)
Community Wiki answer generated from a comment on the question by ypercube



From an MSDN Forums thread:


  HTDELETE  
  
  SQL Server 2014 now uses one shared hash table instead of per-thread copy.
  This provides the benefit of significantly lowering the amount of memory
  required to persist the hash table but, as you can imagine, the multiple
  threads depending on that single copy of the hash table must synchronize with
  each other before, for example, deallocating the hash table. To do so, those
  threads wait on the HTDELETE (Hash Table DELETE) wait type.


(This only applies to hash operators that execute in batch mode)