Andy Mallon talks about plan handles (sql_handle):
If you’ve ever looked at sys.sysprocesses or sys.dm_exec_requests (or a number of other DMVs), you’ve noticed there is a column called “sql_handle” that contains some binary gobbledygook. Books Online gives the (un)helpful definition as “Hash map of the SQL text of the request.”
“Binary gobbledygook” is probably the best description of the plan handle available.