if an aircraft lands with a clearance but the ATCO doesn't get a readback it's an incursion.
How so because if it has been ''cleared to land'' then it is a planned presence and has been authrorised whether the clearance has been readback or not (obviously I'm well aware it is a required readback).
A Runway Incursion is any occurrence at an airport involving the unauthorised or unplanned presence of an aircraft, vehicle or person on the protected area of a surface designated for aircraft landings and departures.