Rhizopogon idahoensis rhi·zo·po·gonidahoensis uncommon noun 1. a large whitish Rhizopogon that becomes grayish brown in maturity SynonymsRhizopogon idahoensis Related words Broader terms false truffle Parts Rhizopogon WordNet 2.1 (Princeton University). WordNet 2.1 Copyright Princeton University. All rights reserved.