1. (n.) Hollowness.

2. (n.) A hollow place; a hollow; as, the abdominal cavity.

abysm abyss alveolation alveolus antrum aperture armpit arroyo basin booth bowl box box canyon breach break broaching canyon cell cellule chamber chap chasm check chimney chink clearing cleft cleuch clough col compartment concave concavity coulee couloir crack cranny crater crevasse crevice crib crypt cup cut cwm deep defile dell depression depth dike dip disclosure ditch donga draw enclosed space excavation fault fenestra fissure fistula flaw flume fold follicle fontanel foramen fracture funnel chest furrow gap gape gash gat gorge groove gulch gulf gully hiatus hold hole hollow hollow shell incision inlet interval joint kloof lacuna laying open leak manger moat notch nullah opening opening up orifice outlet pass passage passageway pew pit pocket pore punch bowl ravine rent rift rime rupture scissure scoop seam shaft shell sink sinus slit slot socket space split stall stoma throwing open trench trough uncorking unstopping vacuity valley vault void vug wadi well yawn yawning abyss