1. most serious or severe in degree, importance, or consequence
Usage: superlative form of grave

Examples

• The doctor delivered the gravest news about her condition.
• This is the gravest threat our nation has ever faced.
• He spoke in his gravest tone about the company’s future.
• The gravest mistake would be to ignore the warning signs.
• She reserved her gravest concerns for the final meeting.
• The gravest consequences will fall on future generations.