Spirochaetaceae spi·roc·hae·taceae uncommon noun 1. large coarsely spiral bacteria; free-living in fresh or salt water or commensal in bodies of oysters Synonymsfamily Spirochaetaceae Related words Broader terms bacteria family Parts Spirochaetales Part of Spirochaeta WordNet 2.1 (Princeton University). WordNet 2.1 Copyright Princeton University. All rights reserved.