Atrophy was a wasting or decrease in size of a body organ or tissue because of disease or lack of use.
In 2268, Dr. Leonard McCoy claimed that the mental faculties of Sigma Draconis VI residents seemed to be almost atrophied because of non-use, explaining Kara's simple mental functions. (TOS: "Spock's Brain")
In 2374, Paris told The Doctor that his holographic 1969 Chevrolet Camaro was experiencing atrophied shocks which needed to be extracted to prevent chrome abrasion, as an excuse for letting his medical studies lapse. (VOY: "Vis à Vis")