光头 is casual and can sound blunt when referring to someone's baldness. It's also used as a modifier: 光头和尚 (bald monk, redundant but emphatic). In gaming slang, 光头 refers to getting nothing — 'going home bald-headed' (empty-handed).
memory
光 means 'bare/smooth' (nothing on the surface) + 头 (head) = a head with nothing on it. Same 光 as in 光脚 (barefoot) and 光膀子 (bare-chested).
