A Hair-do (or don't) featuring one continously pasted together segment of hair covering the entire head; Hair that is so greased and/or gelled that it has no independant movement and creates a "shell" around the head. Popular adhesives include, Hair "Dressing" Hair Gel, Relaxer, Gerri-Curl, ect.
"The wind is blowing 40mph and her hair hasn't budged; It truly is a grease helmet."
"My God Dave! Do you think you could have anymore Murphy's hair dressing on that grease helmet of yours?"