Personality features that resemble a disorder but don't reach the threshold for a diagnosis — fewer criteria met, less impairment, or shorter duration. Common, real, and still capable of causing relational harm.
Your mother has narcissistic traits — entitlement, image-management, weak empathy — but not enough that a clinician would diagnose NPD. The traits still hurt the people close to her. "Subclinical" doesn't mean harmless.