Entry 2 senses · 2 variants Webster, 1913 Phrenetic · Phre·net·ic · IPA a. n. 01 a. Relating to phrenitis; suffering from frenzy; delirious; mad; frantic; frenetic. 1. Relating to phrenitis; suffering from frenzy; delirious; mad; frantic; frenetic. 02 n. One who is phrenetic. 1. One who is phrenetic.