To spread over or occupy an area rapidly and in large numbers; to exceed a limit or budget.
From Old English 'over' (across) + 'run' (to move quickly). The word became common in military contexts meaning 'to invade' and later in project management for exceeding timelines.
Overrun has two fascinating meanings—militarily it means to invade, but in project management it means the project 'invaded' your budget—same word, opposite perspectives on whether it's intentional!
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