Unremitting (adjective)

1. Not easing up or letting up.
2. Constant and persistent.

Origin:

From the latin word 'inremissus' meaning 'not slackening or easing'.

Examples:

1. The pain was unremitting and kept her awake all night.
2. The rain was unremitting and lasted for several days.
3. His efforts to solve the problem were unremitting and finally paid off.
4. The traffic was unremitting and made the journey very slow.
5. The noise was unremitting and disturbed her peace and quiet.