'Adversary' in the Bible

to deliver up such a one to the Adversary for the destruction of the flesh, that the spirit may be saved in the day of the Lord Jesus.

Defraud not one another, except by consent for a time, that ye may be free for fasting and prayer, and again may come together, that the Adversary may not tempt you because of your incontinence;

Therefore I do not run without a definite goal; I do not flail around like one beating the air [just shadow boxing].