firm, slicked-back hairstyle
A men's hairstyle where the hair is combed back firmly, often with a wet or glossy look. Associated with a retro 'tough guy' or yakuza image. Wasei-eigo from 'iron permanent'.
wasei-eigo (Japanese-coined English), from iron permanent
He always wears his hair in a slicked-back style.
あの俳優のアイパーがかっこいい。
That actor's slicked-back hair looks cool.