走人 is a colloquial separable verb meaning 'to leave, to get away' or 'to clear out.' It's informal and often used in commands or to express that someone is quitting or leaving a place. As a verb-object compound (离合词), it can split: for example, 走了人 ('has left') or 走不了人 ('can't leave'). The tone can be blunt or impatient.