The Greek noun aphros means foam or froth. It appears only once in the New Testament (Luke 9:39), in the account of the demon-possessed boy: "a spirit seizes him and he suddenly screams; it throws him into convulsions so that he foams at the mouth." Jude 13 uses the related imagery of "wild waves of the sea, foaming up their shame" to describe false teachers.
The aphros of demonic affliction and the aphros of false teaching share a common quality: both are dramatic, attention-grabbing, and empty. Foam has no substance — it is agitated surface with no depth. Jude's "foaming waves" describes people who produce noise and spectacle but leave behind nothing but shame. True spiritual substance, by contrast, is the quiet depth of the Spirit's fruit: love, joy, peace, patience, kindness, goodness, faithfulness, gentleness, and self-control (Galatians 5:22–23).