Invasive describes something that spreads aggressively where it doesn't belong, often causing problems for whatever was there first.

In biology, an invasive species is a plant or animal introduced to a new environment where it multiplies rapidly and crowds out native species. Kudzu, a vine brought from Japan to the United States in the 1800s, became invasive across the South, smothering trees and buildings under thick green blankets. Asian carp, accidentally released into American rivers, became invasive by eating so much food that native fish struggled to survive. Invasive species succeed because they arrive without the natural predators or diseases that kept them in check back home.

The word also describes medical procedures that involve entering the body, like surgery. An invasive procedure might require cutting through skin, while a non-invasive test like an X-ray examines you from the outside.

More broadly, something invasive intrudes where it's unwelcome. Invasive questions pry into private matters. Invasive advertising follows you around the internet. In every case, invasive suggests pushing into spaces without permission or consideration for what's already there.