What does "strike out" mean?

Cancel or erase, as in Strike out that last sentence, please. [Early 1500s]

Begin a course of action, set out energetically, as in Elaine was determined to strike out on her own. [Early 1700s]

Fail in an endeavor, as in His latest business venture has struck out. This usage originated in baseball, where it refers to a batter's failure to put the ball in play (Williams struck out three times in yesterday's game), as well as to a pitcher's success in eliminating a batter (Clemens struck him out again in the fourth inning). [Late 1800s]