If reporters disagree about some point in the hadith, either pertaining to a particular narrator, text or the isnad, and none of the opinions can be preferred over the other, then this leads to uncertainty. Such a hadith is termed mudtarib
Majhul Al Hal:
Majhul Al Hal (integrity unverified) refers to a narrator who has more than one student who transmitted hadiths from him, but hadith critics did not mention anything about his status as a narrator. In other words, a narrator whose reliability is externally evident, but about whose reliability nothing is known.
Mu’dal (confusing/problematic) report can refer to a hadith with an isnad that contains two or more missing consecutive links.
Mu’an’an is a technical term in the science of hadith. It is used to indicate that established transmission methods, e.g. as indicated by terms such as haddathani (he narrated to me), akhbarani (he informed me) or sami’tu (I heard), are not known to have occurred, or have not been observed, between the transmitters of one or more links in an isnad. The method described by the term mu’an’an solely consists of the preposition ‘an ‘on the authority of’. Isnads with one or more times the preposition ‘an between two transmitters are called mu’an’an isnads.
Mudallis refers to a transmitter who (sometimes) transmits with obfuscation in his transmission; either intentionally or unintentionally narrating a hadith in manner that obscures or omits transmitters in the isnad.
Mukhtalit refers to a transmitter who, on account of becoming senile, blind, or because of his books burning, is unable to transmit hadith correctly anymore.
A mursal hadith is when a transmitter cites someone or the Prophet salla Llahu ‘alayhi wa sallam without actually having met him.
Mutaba’at, Tawabi’, Tabi’ is ‘Corroboration,’ or ‘parallelism’ refers to a narration which corroborates that a certain person had heard a hadith from a certain teacher by serving as evidence that a different student had heard the same hadith from that teacher.
A marfu’ hadith is a narration elevated to Nabi salla Llahu ‘alayhi wa sallam. This, as opposed to a mawquf hadith, which is a narration raised to a Sahabi, and a maqtu’ hadith, which is attributed to a Tabi’i.
Hasan is a term describing a hadith that, while not meeting the isnad requirements to be sahih, did not have flaws serious enough to be considered weak or enjoyed some form of bolstering corroboration.
The word tawatur (recurrence) is a mode of transmitting ahadith. Recurrence obtains when a hadith is narrated through so many channels and by so many people that collusion upon forgery is deemed inconceivable (because of the assumption that such a large number of transmitters cannot find ways to conspire amongst themselves); knowledge engendered by this type is considered certain.
Saraqat Al Hadith:
Equipping existing hadiths with one’s own chains of transmission or constructing entirely new chains of transmission was known as saraqat al hadith (appropriating ahadith).
Shawahid (witness narrations) are those ahadith that are narrated from a totally different chains of transmission (with a different Sahabi) but containing the same meaning as the hadith in question and thus bolstering its reliability.
The word ‘ilal is the plural of ‘illah, which means a defect or a flaw. It refers to an impairing defect in the isnad of a hadith that only become evident when that isnad is compared with other chains of transmission for that hadith.
I’tibar (consideration) is the process in which a hadith critic would collect all the reports that a transmitter had narrated from various teachers and then analyze them for corroboration.