What is Cosy ?
Cosy is (adj) comfortable and warm An open log fire always makes a room feel cosy. She wrapped herself up in a blanket and made herself cosy on the sofa. (NOTE: cosier – cosiest. The US spelling is cozy.) (noun) a cover put over something to keep it hot She knitted a tea cosy for her mother. (NOTE: The plural is cosies.)
source: Easier English, Student Dictionary Upper Intermediate Level