They were invasion by definition: Palestinians crossed into Israel, invaded villages and towns. How come it's not an invasion?
Palestinians crossed into israel from israel (occupied territories by israel). How can you invade yourself?
Aim of an invasion is by definition to conquer.
Usually an invasion entails an intent to capture territory and occupy. A suicide terror attack is qualitatively different even if it’s large-scale. The boots on the ground could just as well have been rockets, whereas an invasion needs a longer term presence.