Synonyms for Gray matter:

n.

brain death, mind, cerebral, brain cell, central nervous system, brainstem, cerebral cortex, head, brain damage, cerebellum, brain, thoughts, brainwave. body (noun)
grey matter, grey substance, Substantia Grisea, gray substance.
gray matter (noun)
grey matter, grey substance, Substantia Grisea, gray substance.

Other synonyms:

mind, brain. head. substantia grisea
Substantia Grisea.
Other relevant words:
brain, head, mind, cerebral cortex, cerebellum, central nervous system.