A runway incursion is "any occurrence in the airport runway environment involving an aircraft, vehicle, person, or object on the ground that creates a collision hazard or results in a loss of required separation with an aircraft taking off, intending to take off, landing, or intending to land."
PHAK Ch-14 (30) Runway Incursion Avoidance
AC 91-73B Flight School Procedures During Taxi Operations
AFH Ch-01 (12)
Runway Incursion Avoidance
Runway Safety: Hot Spots List
Cessna SOPM 1-6 Intra-Cockpit Verbal Coordination
Private Pilot ACS Page 15 Task D. Taxiing