Just a guess but in my part of the U.S. ( Oregon ) this would probably be designated (6"-0 ) or 6-inch minus crushed rock. Meaning a well graded crushed rock varying in sieve size from 6-inches down to 0 inches with only a very small fraction smaller than 200 sieve.
These things are generally local slang terms but you can usually find out by calling a local rock supplier or consulting your State Highway specifications.
good luck