The boy has shaggy hair that looks like it hasn't been cut for months.

shaggy 是形容词，由名词 shag（蓬乱的毛发）加上形容词后缀 -y 构成，表示"毛发蓬松凌乱的"或"毛茸茸的"。用来形容头发或动物毛发时，指又长又乱、不整齐的状态。