To renege means to back out of an agreement or go back on a promise. The word also has an archaic definition: to deny or renounce. Shakespeare uses this latter meaning in Antony and Cleopatra.
What is renege, in Shakespeare's Antony and Cleopatra?
In the play, two of Antony's friends, Demetrius and Philo, are discussing Antony's increasing fondness for Cleopatra. Philo, in particular, is worried about "this dotage" that his general has for the Egyptian queen; to him, Antony's passion "o'erflows the measure." He feels that a general's passion is best spent on the battlefield "in the scuffles of great fights" but instead thinks that Antony has renounced all self-control (temper):
Nay, but this dotage of our general's
O'erflows the measure: those his goodly eyes,
That o'er the files and musters of the war
Have glow'd like plated Mars, now bend, now turn,
The office and devotion of their view
Upon a tawny front: his captain's heart,
Which in the scuffles of great fights hath burst
The buckles on his breast, reneges all temper,
And is become the bellows and the fan
To cool a gipsy's lust.