An implant can have many meanings. Overall, it is something that is placed into the body on a permanent or semi-permanent basis. Breast implants would be considered permanent even if they needed to be removed or replaced in the future. A contraceptive implant refers to a method of birth control in which a small implant is inserted in the upper arm. The implant releases hormones to prevent pregnancy.They are not permanent. They require replacement.
More About Implant
A contraceptive implant releases progestational hormones to thicken the cervical mucus and thin the endometrial lining of the uterus. Typically, the implant will also prevent ovulation from occurring, which prevents pregnancy. Implants are a long-term method of birth control, but can be removed at any time.
There are also penile implants for men with ED due to medical reasons.