An expression meaning 'is in the process of doing' used after the stem of verbs that end with する (forming '〜しつつある'); often used in written or formal contexts.
状況は徐々に改善しつつある。
The situation is gradually improving.
新しい考え方が社会に浸透しつつある。
The new way of thinking is becoming widespread in society.
気候変動の影響は明らかに深刻化しつつある。
The effects of climate change are clearly becoming more serious.