add by mixing or blending on or attaching; "work in the butter and the dough will get the right consistency"; "In his speech, the presidential candidate worked in a lot of learned words"
march aggressively into another's territory by military force for the purposes of conquest and occupation; "Hitler invaded Poland on September 1, 1939"
penetrate or assault, in a harmful or injurious way; "The cancer had invaded her lungs"
occupy in large numbers or live on a host; "the Kudzu plant infests much of the South and is spreading to the North"
a noticeable deterioration in performance or quality; "the team went into a slump"; "a gradual slack in output"; "a drop-off in attendance"; "a falloff in quality"
fall heavily or suddenly; decline markedly; "The real estate market fell off"
fall or sink heavily; "He slumped onto the couch"; "My spirits sank"