Something said or done to provoke laughter; especially: a brief oral narrative with a climactic humorous twist. 
Islam does not prohibit joking. It is known through many narrations that Allah's Messenger (ﷺ) approved joking, and he (ﷺ) would himself play and joke with his companions and small children. 
O you who believe! Keep your duty to Allâh and fear Him, and speak (always) the truth. Qur'an surah Ahzab 33:70
Allah said: "Not a word he utters but there is a watcher by him ready (to record it)." Soorah Qaf 50: 18 
Narrated Abu Umamah: The Prophet (ﷺ) said: I guarantee a house in the surroundings of Paradise for a man who avoids quarrelling even if he were in the right, a house in the middle of Paradise for a man who avoids lying even if he were joking, and a house in the upper part of Paradise for a man who made his character good. Saheeh: Abu Daawood and al-Bayhaqee, authenticated by al-Albaanee in as-Saheehah] Abu Dawud 4782(Sunan Abi Dawud 4800 
Three Points about Joking
1) JOKES INVOLVING LIES
Indeed the Prophet (ﷺ) warned us severely against using lies in our joking, with his statement: ويل للذي يحدث بالحديث ليضحك به القوم فيكذب، ويل له، ويل له
“Woe to the one who lies to make people laugh, WOE TO HIM, WOE TO HIM!” This is an authenitc hadeeth found in Sunan Abee Daawood (4990), At-Tirmidhe (#2315), and others. At-Tirmithee called the hadeeth hasan, and Al-Albaanee agreed.
2) EXCESSIVE JOKING
The Prophet (ﷺ) said: لا تكثروا الضحك، فإن كثرة الضحك تميت القلب
“Don’t laugh too much! For verily, excessive laughter kills the heart!” This is an authentic hadeeth found in Sunan Ibn Maajah (#4193). Refer to Silsilat al-Ahaadeeth as-Saheehah (#506).
And he (ﷺ) also said: يا أمة محمد! والله لو تعلمون ما أعلم لضحكتم قليلا ولبكيتم كثيرا
“O Nation of Muhammad! By Allaah, if you knew what I know, you would laugh little and cry much.” Sahih Al-Bukhari 6486 (Vol 8:493)
3) INSULTING PEOPLE IN JEST
Allah says in the Qur'aan: "O you who believe! A group of people should not scorn another group, for it may be that (the scorned person) is better than the other…" [Soorah al-Hujurat (49): 11]
Let us be reminded of Allaah’s ayath: الخبيثات للخبيثين والخبيثون للخبيثات والطيبات للطيبين والطيبون للطيبات
Evil words are for evil men, and evil men are [subjected] to evil words. And good words are for good men, and good men are [an object] of good words. Those [good people] are declared innocent of what the slanderers say. For them is forgiveness and noble provision. [Qur'aan suarh Noor 24:26]
And the speech of His noble Messenger (ﷺ):
من كان يؤمن بالله واليوم الآخر فليقل خيرا أو ليصمت
“Whoever believes in Allaah and the Last Day must speak with goodness or remain silent.” [Sahih Muslim 48 (Book 1:78)] 
Rules of Joking in Islam
Some people joke too much and it becomes a habit for them. This is the opposite of the serious nature which is the characteristic of the believers. Joking is a break, a rest from ongoing seriousness and striving; it is a little relaxation for the soul.
‘Umar ibn ‘Abd al-‘Azeez (may Allaah have mercy on him) said: “Fear joking, for it is folly and generates grudges.”
Imaam al-Nawawi (may Allaah have mercy on him) said: “The kind of joking which is forbidden is that which is excessive and persistent, for it leads to too much laughter and hardening of the heart, it distracts from remembrance of Allaah, and it often leads to hurt feelings, generates hatred and causes people to lose respect and dignity. But whoever is safe from such dangers, then that which the Messenger of Allaah (peace and blessings of Allaah be upon him) used to do is permissible for him.”
Sa’d ibn Abi Waqqaas said: “Set a limit to your jokes, for going to extremes makes you lose respect and incites the foolish against you.”
The amount of joking should be like the amount of salt in one’s food.
The Prophet (peace and blessings of Allaah be upon him) said: “Do not laugh too much, for laughing too much deadens the heart.” (Saheeh al-Jaami’, 7312)
‘Umar ibn al-Khattaab (may Allaah be pleased with him) said: “Whoever laughs too much or jokes too much loses respect, and whoever persists in doing something will be known for it.”
So beware of joking, for it “causes a person to lose face after he was thought of as respectable, and it brings him humiliation after esteem.”
A man said to Sufyaan ibn ‘Uyaynah (may Allaah be pleased with him), “Joking is not right, it is to be denounced.” He replied, “Rather it is Sunnah, but only for those who know how to do it and do it at the appropriate time.”
Nowadays, although the ummah needs to increase the love between its individual members and to relieve itself of boredom, it has gone too far with regard to relaxation, laughter and jokes. This has become a habit which fills their gatherings and wastes their time, so their lives are wasted and their newspapers are filled with jokes and trivia.
The Prophet (ﷺ) said: “If you knew what I know, you would laugh little and weep much.” In Fath al-Baari it says: “What is meant by knowledge here has to do with the might of Allaah and His vengeance upon those who disobey Him, and the terrors that occur at death, in the grave and on the Day of Resurrection).
Muslim men and women have to be inclined to choose righteous and serious friends in their lives, who will help them to make good use of their time and strive for the sake of Allaah with seriousness and steadfastness, good and righteous people whose example they can follow. Bilaal ibn Sa’d said: “I saw them [the Sahaabah] jokingly pretending to fight over some goods, and laughing with one another, but when night came they were like monks.”
Ibn ‘Umar (may Allaah be pleased with him) was asked, “Did the Companions of the Prophet (ﷺ) laugh?” He said, “Yes, and the faith in their hearts was like mountains.”
So you have to follow the example of such people, who were knights by day and monks (i.e., devoted worshippers) by night.