To make deep or deeper; to sink lower; as, to deepen the channel of a river or harbor; to deepen a well.

To make dark or darker; to make more thick or gloomy; as, to deepen the shades of night; to deepen gloom.

To give a darker hue, or a stronger color; as, to deepen a color; to deepen a red, blue or crimson color.

To make more poignant or distressing; as, to deepen grief or sorrow.

To make more frightful; as, to deepen the horrors of the scene.

To make more sad or gloomy; as, to deepen the murmurs of the flood.

To make more grave; as, to deepen the tones of an organ.

To become more deep; as, the water deepens at every cast of the lead.