Hair that has been left to twist and mat together into long, thick, rope-like pieces. You don't cut hair into dreadlocks — you stop combing it apart, and over months the strands lock together on their own. The word is almost always plural, because you have a whole head of them, not one; 'a dreadlock' sounds odd unless you really mean one single piece. People shorten it to 'dreads' in everyday talk, and 'locs' is now the common spelling among Black people who wear them, especially in America. The style is tied to Rastafarians in Jamaica, where it carries religious meaning, but plenty of people wear it with no religion attached — musicians, athletes, anyone who likes it. That's where the word gets touchy: because the hairstyle grew out of Black culture and Black hair texture, whether other people should wear it is an argument that still runs, and you will hear the phrase 'cultural appropriation' near this word. As a verb you can 'dreadlock' hair, though most people just say 'have dreads' or 'grow dreads'.