Drop Out Meaning

(idiomatic) Prematurely and voluntarily leave (school, a race, or the like).

Example: Used other than as an idiom: see drop,‎ out.
1922, Margery Williams, The Velveteen Rabbit
  Generally, by the time you are Real, most of your hair has been loved off and your eyes drop out and you get loose in the joints and very shabby.
  Nothing went well in high school, so he dropped out.