grawlix

noun /ˈɡrɔːlɪks/

a) A spiral-shaped graphic used to indicate swearing in comic strips.

He does all the Popeye voices, but prefers Olive Oyls. He has noises for the nittles, the grawlix, the quimps, the jarns. He blows each balloon up before your ears. He reels home, +s on his eyes, singing the spirl that rises like heat from his head.

b) A string of typographical symbols, especially "\@$%&!", used (especially in comic strips) to represent an obscenity or swearword.