Definition of a ghareeb hadeeth
Question

                What is a ghareeb hadeeth? Please advise us, may Allah reward you with good.
Praise be to Allah.
      A ghareeb 
      hadeeth is one in which there is some kind of uniqueness. There are many 
      kinds of uniqueness, the most important of which are two: 

    1 - Absolute 
    uniqueness, which is where a particular narrator - at any stage of the 
    isnaad - is the only one who narrated this hadeeth, and no one else narrated 
    it alongside him. So in this case the ghareeb hadeeth is one which is only 
    known to be narrated from the Prophet with one isnaad. 

    An example of 
    this is the hadeeth “Actions are but by intentions.” This hadeeth has only 
    one proper isnaad. It was narrated by Yahya ibn Sa‘eed al-Ansaari, from 
    Muhammad ibn Ibraaheem al-Taymi, from ‘Ilqimah ibn Waqqaas al-Laythi, from 
    ‘Umar ibn al-Khattaab. 

    2 - Relative 
    uniqueness, which means that one of the narrators of a particular hadeeth 
    was the only one to narrate it from his shaykh, and no one else narrated it 
    from his shaykh, even though the hadeeth was narrated via a number of 
    isnaads, but none of his students narrated the hadeeth from him except one 
    narrator.  

    An example of 
    this is the hadeeth narrated by ‘Eesa ibn Moosa Ghunjaar, from Abu Hamzah 
    al-Sukkari, from al-A‘mash, from Abu Ayyoob al-Sakhtiyaani, from 
    Muhammad ibn Sireen, from Abu Hurayrah, who said: The Prophet (blessings and 
    peace of Allah be upon him) said: “Do not call grapes al-karm.” 

    Al-Tabaraani 
    said: No one narrated this hadeeth from al-A‘mash except Abu Hamzah 
    al-Sukkari. 

    See how Abu 
    Hamzah al-Sukkari was the only one who narrated this hadeeth from al-A‘mash, 
    so his uniqueness is in relation to his shaykh al-A‘mash, but it is not 
    absolute uniqueness, as the hadeeth was narrated via many isnaads from a 
    number of the Sahaabah. 

    And Allah knows best.