King Piccolo's kanji, 魔, pronounced ma and meaning "demon", "devil", or "evil spirit". King Piccolo wears this kanji on the front of his uniform, as does Piccolo Jr. as a young child. Piccolo Jr. also gives Gohan this kanji while under his training. The word majin also borrows from this symbol (meaning the same things).
(According to dragonball.wikia)