1. to stop developing, growing, or making progress
2. to become motionless or still, especially of water or air

Examples

• The economy began to stagnate during the recession.
• Her career stagnated after she stopped taking on new challenges.
• Without fresh ideas, the company’s growth will stagnate.
• The water in the pond tends to stagnate in summer.
• Air can stagnate in poorly ventilated rooms.
• His skills stagnated because he never practiced.
• The negotiations stagnated when neither side would compromise.