1Damp or humid — describing something that contains moisture or feels slightly wet.
梅雨で部屋が湿っぽい。
The room is damp because of the rainy season.
洗ったままの服が湿っぽい匂いがする。
The washed clothes have a damp smell.
この本、湿っぽくてページがくっついている。
This book is damp and the pages are sticking together.
2Gloomy or melancholic — describing a mood, tone, or story that is sad, soppy, or heavy.
彼は湿っぽい話ばかりして、場の雰囲気が暗くなる。
He keeps telling gloomy stories and the mood becomes heavy.
あの映画は湿っぽい恋愛描写が多い。
That film has a lot of soppy/melancholic love scenes.