Stagnate (verb)

1. Stop making progress or developing; become stagnant.
2. Become stale, stagnant, or blocked; stop flowing.
3. Fail to develop or improve.

Origin:

From the latin word "stagnare" which means to be still or stagnant, it refers to stop making progress or developing, to become stagnant.

Examples:

1. The economy has been stagnating for the past year.
2. The water in the pond had stagnated and was not safe to drink.
3. The company's profits have stagnated and they are not growing.
4. The project has stagnated because of lack of funding.
5. The negotiations have stagnated and no progress has been made.