| Aquifer | A water bearing stratum of rock, sand, or gravel, that yields water to a well or spring. |
| Boxwork | Intersecting mineral blades projecting from the walls or ceiling of a cave. |
| Breakdown | Rock slabs, blocks, or chips on the floor of a cave that have fallen from the walls or ceiling. |
| Cable Ladder | A ladder made of two parallel cables with metal rungs held in place on the cables by metal ferrules crimped to the cable. |
| Calcite Raft | A thin layer of crystalline carbonate material that floats on the surface of a still cave pool. |
| Carbide Lamp | A lamp that produces light by burning acetylene gas produced from carbide and water. |
| Cave | A naturally formed void in the earth, generally large enough for a person to enter. |
| Caver | A person who explores caves in a safe manner while showing respect for the cave, other cavers, the land above the cave, and the cave owner. |
| Cavern | A large cave. |
| Chert | A hard mineral composed of silica, usually light-cream or gray to black in color. |
| Column | A speleothem formed when a stalagmite and a stalactite grow together. |
| Dolomite | A rock or mineral composed of calcium magnesium carbonate, CaMg(CO3)2. |
| Dome | A high shaft in a room or passage when seen from below. |
| Electric Lamp | In the context of caving, generally a helmet-mounted headpiece (bulb, reflector, and lens) with a wire running to a battery carried elsewhere on the person. |
| Flagging Tape | Thin plastic ribbon of any color used for marking survey stations, trails, etc. |
| Flowstone | Mineral deposits that have accumulated as water slowly seeps over a wall or floor of a cave. |
| Formation | A rock unit with distinct characteristics within a sequence of rocks. A term for mineral deposits in caves. |
| Grotto | An internal organization of the National Speleological Society made up of individuals who reside in the same general locality. A chapter |
| Gypsum | A common cave mineral composed of hydrous calcium sulphate, CaSO4.2H2O |
| Gypsum Flower | A fibrous speleothem of sulfate that radiates out in "petals" from a common base. |
| Gypsum Needle | A sulphate speleothem having the shape of a needle that grows gypsiferous cave soils. |
| Helectite | A smooth-surface stalactitic form that grows curved paths instead of hanging vertically. |
| Hypogenic Cave | A cave that forms as a result of water rising from deep within the earth. |
| Hypothermia | A dangerous condition caused by wet and cold. A common complication of a cave accident or of not dressing properly for the cave. |
| Joint | A fracture in a series of rock units, generally at an angle to the bedding planes. |
| Karst | A terrain where the topography is formed by the dissolving of rock, usually limestone or gypsum, and is characterized by solutional surface features, subterranean drainage, and caves. |
| Limestone | A grey-blue rock composed of calcium caronate,CaCO3 |
| Onyx | A banded flowstone. |
| Pit | A shaft in a cave when seen from above or an open-air shaft that serves as the entrance to a cave. |
| Pit Cave | A cave that must be entered through a pit, usually requiring vertical techniques to descend and ascend. |
| Botryoid | Small bead- or knob-like projections from cave walls. |
| Popcorn | A botryoidal form resembling popcorn. |
| Potholes | Bell hole-like structures in passage floors. |
| Rimstone Dam | A wall-shaped calcite deposit that impounds, or formerly impounded, pools of water. |
| Scallops | Oval hollows forms on walls and streambeds by flowing water, These hollows have an asymmetric cross section and can be used to determine the direction of water flow. |
| Shaft | A vertical cave passage, a pit. |
| Shield | A massive plate or slab of travertine that juts out from the cave wall at an angle apparently determined by the arrangement of joints. |
| Sinkhole | A depression in the ground caused by solution of the underlying rock or collapse of the roof of an underlying cavern. |
| Sinking Stream | A stream that disappears underground, usually in a depression. |
| Soda Straw | A thin hollow stalactite resembling a sipping straw. It grows from the tip by water flowing down the inside. |
| Speleogenesis | The process by which a cave forms. |
| Speleothem | A secondary mineral deposit formed in caves such as stalactites and stalagmites. |
| Spelunker | A term usually used by non-cavers to mean a caver. |
| Spongework | A highly complicated system of tiny holes, tubes, and interconnected cavities found on cave walls that can resemble Swiss cheese. |
| Squeeze | In the context of caving, a very tight passageway. |
| Stalactite | A speleothem of cylindrical or conical shape hanging from a ceiling or ledge resembling icicles. |
| Stalagmite | A speleothem of cylindrical or conical shape rising from a floor or ledge. |
| Sump | A place where the ceiling of a passage drops to and below the water level, leaving no air space, with the cave passage continuing under water. |
| Syphon | In the context of caving, a sump. |
| Travertine | Calcium carbonate which is deposited from ground water in a series of flowstone dams - any flowstone or dripstone deposit. |
| Troglobite | An animal that is fully adapted to life in total darkness and can only live underground. |
| Trogophile | An animal that may live underground but may also be found on the surface. |
| Trogloxene | An animal that visits caves for a part of their activities. |
| Virgin Passage | A cave passage ( or entire cave ) that has not previously been entered, a new discovery. |
| Water Table | The top or highest level of ground water in a given area. Below this level cave passages may be flooded. |
| Webbing | Flat or tubular nylon strapping. |