IRRUPTION n. 2 definitions
A bursting in; a sudden, violent rushing into a place; as, irruptions of the sea. Lest evil tidings, with too rude irruption Hitting thy aged ear, should pierce too deep. Milton.
IN- prep.
in- regularly becomes il- before l, ir- before r, and im- before a labial; as, illusion, irruption, imblue, immigrate, impart. In- is sometimes used with an simple intensive force.