What does the word `Abd (worshipper) mean?

The word Abd[1] means the subdued or subjugated. This meaning encompasses all sorts of creation: higher and lower, rational and reasonless, animate and inanimate, dynamic and static, apparent and hidden, believing and disbelieving, and pious and dissolute, etc.; all of which are created by Allah he Almighty. 

They are subjected to Him, and managed by Him Alone. Moreover, all of them have a limit and destination and each one runs (its course) or an appointed term. Such is the judgment and ordering of (Him), the Exalted in Power, the Omniscient. And if the intended sense is the modest God-loving worshiper), in this case it refers only to the believing men and women who are Allah's honorable slaves and pious godly ones; on them shall be no fear, nor shall they grieve.