An accomplishment is something notable that you've done. Graduating from college with honors is an accomplishment.
First used in the 15th century, the noun accomplishment derives from the Old French word acomplir, meaning "to fulfill, fill up, complete." An accomplishment is something you've completed successfully. The word often refers to a goal that you've achieved. If you're a runner, you'd consider completing a marathon to be a great accomplishment. Gaining a new skill can also be an accomplishment. Speaking French fluently might be an accomplishment that makes you really proud.