sacculusPronunciation: /ˈsakjʊlʊs/Definition of sacculus noun Anatomy the smaller of the two fluid-filled sacs forming part of the labyrinth of the inner ear (the other being the utriculus). It contains a region of hair cells and otoliths which send signals to the brain concerning the orientation of the head. another term for saccule.Origin: mid 18th century: from Latin, diminutive of saccus 'sack'sacculus in other Oxford dictionaries Definition of sacculus in the US English dictionary