Slightly cold; a bit chilly — used for weather or a place that feels a little cold, and sometimes figuratively for an uneasy feeling.
今朝は薄寒くてコートを羽織った。
It was a bit chilly this morning, so I put on a coat.
部屋の中なのに薄寒いので暖房をつけた。
Even inside the room it felt a little chilly, so I turned on the heater.
その話を聞いて薄寒い気持ちになった。
Hearing that story gave me a slightly chilling/uneasy feeling.
秋の薄寒い風が吹き始めた。
The slightly chilly autumn wind began to blow.