管闲事 is a separable verb (离合词) meaning 'to meddle' or 'to poke one's nose into others' affairs'. The verb 管 ('to take charge of') and the object 闲事 ('unimportant business') can split when inserting measure words, modifiers, or aspect markers — e.g., 管什么闲事 ('what business is that of yours?'), 管了太多闲事 ('meddled too much'). It is commonly used in negative phrases like 多管闲事 ('being a busybody') and 别管闲事 ('mind your own business').