There are various synonyms for the phrase "become less flexible." Some words that could be used to describe this state include inflexible, rigid, stiff, unbending, immobile, unyielding, and inelastic. When a person becomes less flexible, their movements become restricted, and they may find it harder to perform physical tasks. This loss of flexibility can be caused by factors such as aging, injury, or a sedentary lifestyle. It is important to maintain flexibility through regular exercise and stretching, as this can improve overall health, reduce the risk of injury, and enhance physical performance. By staying active and practicing good posture, individuals can avoid becoming less flexible over time.