It means the same thing in medical terms that it means in general use: something that naturally happens along with something else.
Concomitant is an adjective meaning "naturally associated with."
Concomitant
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."
Stasis is the medical term meaning stopping.
Strabismus is the medical term meaning cockeye.
Kyphotic is the medical term meaning humpbacked.