irrupt

Concise Oxford English Dictionary © 2008 Oxford University Press:
irrupt /ɪˈrʌpt/

▶verb

• 1 enter forcibly or suddenly.

• 2 (chiefly of a bird) migrate into an area in abnormally large numbers.

– derivatives
irruption noun,
irruptive adjective.

– origin C19 (earlier (C16) as irruption): from L. irrupt-, irrumpere ‘break into’.