Sieve-like; cribriform: in anatomy specifically applied to a bone of the skull. See II.Specifically, pertaining to the ethmoid: as, the ethmoid region of the skull.n. A bone of the cranium, situated in the middle line of the skull, in advance of the sphenoid, above the basicranial axis, transmitting the filaments of the olfactory nerve, and constituting the bony skeleton of the organ of smell: so called because, in the human subject and mammalia generally, it has a cribriform plate perforated with numerous holes for the passage of the olfactory nerves.