In a manner that is dense or closely packed together. The fog lay thickly over the valley, obscuring the view of the mountains.
In a way that forms a thick layer or coating. She spread butter thickly on the toast.
In a manner that is heavily or abundantly covered. The trees were thickly covered with snow after the storm.
In a way that is not clear or is difficult to understand, often due to an accent or speech impediment. He spoke thickly, his words slurred from the effects of the cold.