stagnate
/ˈstæɡneɪt/
verb
- To stop flowing or moving, especially of water or air; to become stale or dirty.
- The air in the basement stagnated because there were no windows.
- The river began to stagnate after the dam was built upstream.
- If the water in the birdbath is not changed regularly, it will stagnate.
- To stop changing or developing; to become inactive or dull.
- The company's growth stagnated after the founder left.
- Without new challenges, your skills can stagnate.
- Their relationship stagnated because they stopped communicating.