The word Shaytan is derived from the roots (شطن) and شاطن means 'impure and base'.
Shaytan refers to an entity that is rebellious - irrespective of whether it is of the humans, jinn or animals. It is also said to mean 'a nefarious soul, who is distanced from Allah (s.w.t.) and Truth'; all of these meanings, in reality, can be observed to be turning back to one common element.
It should be noted that Shaytan is a 'common noun' whereas Iblis is a 'proper noun'. In other words, every harmful, deviating and rebellious entity - human or otherwise - is referred to as Shaytan. Iblis is the name of that Shaytan, who deceived Adam and even presently, together with his soldiers and forces, lies in ambush of the humans.
From the usage of this word in the Qur’an, it can also be inferred that Shaytan is used to denote a harmful being - one who has deviated from the right path and has embarked upon a mission of distressing others; an entity that attempts to create division, discord and corruption, just as we recite:
إِنَّمَا يُرِيدُ الشَّيْطَانُ أَنْ يُوقِعَ بَيْنَكُمُ الْعَدَاوَةَ وَ الْبَغْضَاءَ
“Surely Shaytan only desires to cause enmity and hatred to spring in your midst.”1
The word يُرِيدُ is in the imperfect tense which denotes 'continuity', indicating that this 'desire' is a continuous and perpetual desire of the Shaytan.
Furthermore, we observe that in the Qur’an, the use of the term Shaytan has not been restricted for a specific being; rather it has been used to refer to wicked and corrupt humans too. The Qur’an says:
وَ كَذٌلِكَ جَعَلْنَا لِكُلِّ نَبِيٍّ عَدُوًّا شَيَاطِينَ الإِِنْسِ وَ الْجِنِّنِ
“And thus did We make for every prophet an enemy, the Shaytans from among men and jinn.”2
That Iblis has also been referred to as Shaytan is because of the evilness and corruption that exists within him.
In addition to this, the word Shaytan has been employed to refer to microbes too:
For example, the Commander of the Faithful (a.s.) has said:
لاَ تَشْرَبُوا الْمَآءَ مِنْ ثُلْمَةِ الإِِنَاءِ وَ لاَ مِنْ عُرْوَتِهِ فَإِنَّ الشَّيْطَانَ يَقْعُدُ عَلَى الْعُرْوَةِ وَ الثُّلْمَةِ.
“Do not drink water from the broken portion of the vessel nor from the portion of the handle, for surely, the Shaytan sits upon the handle and the broken portion.”3
Imam as-Sadiq (a.s.) has also said:
وَ لاَ يُشْرَبُ مِنْ أُذُنِ الْكُوزِ وَ لاَ مِنْ كَسْرِهِ إِنْ كَانَ فِيهِ فَإِنَّهُ مَشْرَبُ الشَّيَاطِينِ.
“(Water) should not be drunk from the handle (side) of a jug and nor from the broken portion of it, if present, for these are the drinking-place of the 'Shaytans'.”4
The Noble Prophet (S) has said: “Do not lengthen (the hair of) your moustaches, for the Shaytan makes it a haven for himself and conceals himself there!”5
Thus, it becomes clear that one of the meanings of Shaytan is 'harmful microbes'. Nevertheless, this does not mean that it possesses this meaning on all occasions and in all instances. Rather, it means that Shaytan has several meanings, one of the most obvious of them being 'Iblis and his assistants'; another being 'corrupt humans'; while at times it is also employed to refer to 'harmful bacteria'.6