Synonyms of the word

untiring

• adj. Not able to be tired; inexhaustible.
• adj. Unfailing; resolute.

diligent

• adj. Performing with intense concentration, focus, responsible regard.

hardworking

• adj. Of a person, taking their work seriously and doing it well and rapidly.

industrious

• adj. Hard-working and persistent.

tireless

• adj. Indefatigable, untiring and not yielding to fatigue.
• adj. Without a tire (wheel covering); tyreless.