Definitions of lengthen

1. To make or grow longer; extend; protract.

2. To extent in length; to make longer in extent or duration; as, to lengthen a line or a road; to lengthen life; - sometimes followed by out.

3. To make long or longer.

4. To become longer.

5. To grow longer.

6. become long or longer; " In Spring, the days lengthen"

7. To make, or become, longer.

8. To extend in length; to elongate; to draw out.

9. To make longer; to draw out; to grow longer.