Plain English Meaning
A situation where something is wrong on board that either needs help right now (distress) or will need help soon if it isn't sorted out (urgency). Both count as emergencies in aviation.
Full Definition
A distress or urgency condition. A distress condition exists when an aircraft is threatened by serious and/or imminent danger and requires immediate assistance. An urgency condition exists when an aircraft is concerned about safety and requires timely but not immediate assistance — a potential distress condition.
Context Anchor
Pilots encounter this term in radio communication, abnormal procedures, accident and reporting, and guidance about distress or urgent situations.