The Meaning of Obscenity and Profanity
Fuhsh linguistically: is everything that exceeds its limit, referred to as fahish (obscene). Fuhsh, fahsha’, and fahishah all describe ugly speech and actions. Their plural is fawahish.  Mukhtar al-Sihah, al-Razi (p. 243).
Fuhsh technically: is what is disliked by nature of lowly external deeds, as well as disliked by the intellect and looked down upon by the Law. The three signs of Allah unite in its dismissal: Law, intellect, and nature. Through this discernment a deed is described as obscene.  Lisan al-`Arab, Ibn Manzur (6/325).
Badha’ah linguistically: is obscenity. Fulanun badhi’ al-lisan (so-and-so is foul-mouthed) wa al-mar’atu badhi’ah (the woman is profane) comes from badha’ah (foulness). It is bad, ugly language.  al-Tawqif `ala Muhimmat al-Ta`rif, al-Manawi (p. 257).
Badha’ah technically: is describing indecent things with direct language.  al-Kulliyyat, al-Kafawi (p. 243). The Difference between Obscenity, Ugliness (Qubh), and Cursing (Shatm)  Mufid al-`Ulum wa Mubid al-Humum, al-Khawarizmi (p. 225); al-Furuq al-Lughawiyyah, al-`Askari (p. 367).
That which is obscene is intensely ugly. Furthermore, ugliness is used to describe appearances. It is said, for example, ‘Monkeys are ugly,’ but it is not said, ‘They are obscene.’ One may say ‘Obscenely ugly, tall, etc.’ Anything that has severely exceeded its limit is obscene. This is not true for ugliness. Obscenity is to describe some act in an ugly way, while cursing is attributing someone to that.Dispraise of Obscenity and Profanity in the Qur’an and Sunnah
❖ Allah, sanctified, said: “Allah does not like bad words to be made public unless someone has been wronged: He is all hearing and all knowing.” al-Nisa’: 148.
❖ Allah, most honourable, said: “Say: ‘My Lord only forbids disgraceful deeds- whether they be open or hidden- and sin and unjustified aggression, and that you, without His sanction, associate things with Him, and that you say things about Him without knowledge.’” al-A`raf: 33.
❖ `Abdullah ibn Mas`ud, Allah be pleased with him, said: “The Messenger of Allah ﷺ said: ‘The believer is not one who maligns or curses, nor is he obscene or profane.’”  Reported by al-Tirmidhi (1977) and Ibn Hibban (192). al-Tirmidhi said: “It is sound, strange.” al-Hakim authenticated according to the conditions of the Two Sheikhs in al-Mustadrak (1/57). al-`Iraqi authenticated its chain in Takhrij al-Ihya’ (p. 1010).
❖ Abu al-Darda’, Allah be pleased with him, narrates that the Prophet ﷺ said: “There is nothing heavier in the scale of the believer on the Day of Resurrection than good moral character - Allah hates the obscenely profane.”  Abu Dawud reported it from various paths (4799) and al-Tirmidhi (20-2), and the wording is his. al-Tirmidhi said: “It is sound, authentic.” al-Albani authenticated it in Sahih Sunan al-Tirmidhi (2002). Quotes of the Predecessors and Scholars on Dispraising Obscenity and Profanity  al-Samt, Ibn Abi al-Dunya (p. 89, 185).
❖ `Abdullah ibn Mas`ud said: “The most ignoble of man’s traits is obscenity.”
❖ `Awn ibn `Abdillah, Allah have mercy upon him, said: “Verily obscenity and profanity are hypocrisy. They increase in this world but take away from the next, and what they decrease therein is greater than anything they increase here.”
❖ al-Ahnaf ibn Qays, Allah have mercy upon him, said: “Shall I not inform you of the worst of ailments? A profane tongue and lowly character.”Impacts and Harms of Obscenity and Profanity
The profane is deserving of Allah’s punishment in the worldly life as well as the next life. People avoid him due to his tongue. They are signs of hypocrisy. It is not one of the signs of complete faith. Allah hates the obscene. The obscene is far from Allah and the people. Means to Desisting from Obscenity and Profanity
Remembering Allah, exalted, often. Adhere to silence. Habituating the tongue to say beautiful things. Avoiding ugly wording even if it is referring to true things, preferring instead hints or metaphors.  Adab al-Dunya wa al-Din, al-Mawardi (p. 284). Avoiding speaking about that which does not concern one. That one does not accustom himself to damn animals and places. Adorning oneself with bashfulness. Befriending good company and spending time with them. Reasons for Falling into Obscenity and Profanity  al-Dhari`ah ila Makarim al-Shari`ah, al-Raghib (p. 284); Afat al-Lisan, Ibrahim al-Mashukhi (p. 108 - 109).
Malignance and ignobility. Harmful intent. Being habituated to deal with miscreants. Dispraise of Obscenity and Profanity in Poetry
Talhah ibn `Ubaydillah said:
“Do not hasten to anyone unjustly
For tyranny’s end is most repulsive.
Be not profane even if outraged
With another - obscenity is ignobility.”  al-Hilm, Ibn Abi al-Dunya (p. 73).