In-flexible, which means unwilling to change or bend, has several antonyms that imply adaptability and flexibility. One antonym is flexible, which refers to the ability to adjust to new situations, ideas, and people. Another antonym is adjustable, which connotes the capacity to change or be modified to fit different requirements or conditions. Accommodating is another antonym that suggests a willingness to make allowances or compromises for others. Another antonym is pliable, which refers to the capacity to be easily shaped or molded, and is often used in a metaphorical sense to describe someone open to change or influence. Lastly, another antonym for in-flexible is fluid, implying a state of constant change or movement.