1. superlative form of lengthy; having the greatest length in time or physical extent
Usage: superlative form

Examples

• The lengthiest speech of the evening lasted over two hours.
• This is the lengthiest book in the series.
• The lengthiest part of the journey was the flight across the Pacific.
• She gave the lengthiest explanation of all the candidates.
• The lengthiest delay occurred during the third act.
• His lengthiest essay earned him the highest grade.