To sublet is to rent out to a third person a place that you yourself are renting from someone else. You are the tenant, and for a while you become a small landlord: you keep your lease with the owner, and you take rent from the new person. Students do it when they go home for the summer; workers do it when they are sent abroad for six months. It is also a noun — 'I found a sublet near the station' means a place available on this kind of arrangement — and the person taking it is a 'subtenant', or in American English a 'subletter' or 'subleaser'. The verb form is irregular in a way that catches everyone: sublet, sublet, sublet, like 'let' itself. Never 'subletted'. The '-ting' form doubles the t: 'subletting'. One important real-world point that dictionaries often skip: in many places you are not free to do this. Most leases say you must ask the owner first, and subletting without permission can get you thrown out. So when people talk about a sublet, the question 'does the landlord know?' is usually right behind it. In American English you will hear 'sublease' just as often, and for ordinary purposes the two mean the same thing.