We don't have synonyms for claustrum yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are claustral, castrum and lustrum.
(n) :
(neuroanatomy) A thin, irregular sheet of grey matter underneath the inner part of the neocortex on both sides of the brains of mammals; its exact function is not understood, but it is believed to facilitate coordination between senses
(n) :
(neuroanatomy) A thin, irregular sheet of grey matter underneath the inner part of the neocortex on both sides of the brains of mammals; its exact function is not understood, but it is believed to facilitate coordination between senses