1. not having official authority or approval; not formally recognized
2. done or said in a private capacity rather than in an official role

Examples

• The unofficial results showed her winning by a large margin.
• He gave me some unofficial advice about the job application.
• The meeting was unofficial, so no minutes were taken.
• She spoke to reporters in an unofficial capacity.
• The unofficial dress code allows jeans on Fridays.
• His unofficial role as team leader was widely recognized.
• The unofficial estimate put the crowd at over 10,000 people.