It's called the coccyx and is made up of four very small vertebrae.
The medical term meaning pertaining to the tailbone is coccygeal. The proper name for the tailbone is coccyx.
The medical term meaning pertaining to the direction of the tailbone is "caudal." This term is used to describe structures that are situated closer to the tailbone or tail end of the body in anatomical orientation.
The medical term for the five fused vertebrae above the tailbone is the sacrum.
The tailbone defines the coccygeal region. The sacral region is another term that might be used.
The caudal area is the medical term meaning tail region, although in humans it may be called the coccygeal region. Cauda means tail, and coccyx is tailbone.
Anacusis is the medical term meaning complete deafness.
Syncope is the medical term meaning fainting.
Lamina is the medical term meaning layers.
Sensation is the medical term meaning feeling.
Eructation is the medical term meaning burping.eructation
Atrophy is the medical term meaning shrinking.
Metastasize is the medical term meaning "to spread."