My sources are basically some posts from other forums, who posted some fatwas of contemporary scholars (like ar-Rahyly -who quoted a fatwa of- a-Shanqyty and as-Sahym) and this (Arabic) fatwa!
الجُمْهُور (jumhoor) with its plural جَمَاهِير (jamaaheer) basically meaning the assemblage basically in Arabic language is used to describe a majority or major part of something (see also in AR-AR-Dictionary). Ibn Mandhor said it refers to majority of a thing or most of the people. While jamaaheer is often used to refer to the noblest among the people.
Meaning of jumhoor جُمْهُور in fatwas
So if it is said that the majority (jumhoor) of the scholars have a certain opinion about a rule it means that 3 of 4 madahabs have the same opinion. For example if abu Hanifa, Malik and Ahmad had an opinion while a-Shafii had a different opinion.
Other examples of the meaning of an opinion or ruling stated by al-jumhoor:
As above if the hanafi, maliki and shafi'i school had a view saying something is allowed while only the hanbali school say's it is not or it is makrooh, than scholars would say the jumhoor say this is allowed.
However jumhoor doesn't exclude some exceptions for example: the hanafi, the maliki have an opinion on a matter, saying it is allowed, while the shafi'i and hanbali say no or say it is makrooh, but if the companions of a-Shafi'i were aside the hanafis and malikis scholars would also say al-jumhoor allowed it, as the companions have differed to the saying of their Imam.
A more realistic example: Scholars say that the tawaf al-wada' طواف الوداع (Farewell Tawaf) is considered as wajib by al-jumhoor: meaning by the hanafi, shafi'i and hanbali school, while those who say it is only sunnah are the maliki school, Imam a-Shafi'i himself, and one of two statements of Imam Ahmad, here the majority says it is wajib.
Meaning of jamaaheer جَمَاهِير in fatwas
In case that scholars used this term they mean that those who differed from the opinion could be counted, one could say it is close to Ijma' , this means most of the scholars except al-Ghazaly had a certain opinion or are in consensus about a certain ruling or verdict.
Note that some scholars also in this case use the term the most al-akthar الأكثر as a synonym for jamaaheer, while they use many, al-katheer الكثير as a synonym of jumhoor.
There's an other technical term which is: the most correct الأصح (al-assah) and the correct الصحيح (as-sahih). So if they said a certain opinion is أصح (assah) the most correct than the "opposed view" is correct, while this certain view is better or more correct. While if they say a certain view is صحيح (sahih) than the "opposed view" is weak!
For Ijma' take a look at this fatwa explaining it:
Shaykh Ibn ‘Uthaymeen (may Allah have mercy on him) said:
In linguistic terms, ijmaa‘ means resolve and agreement.
In shar‘i terms, it means the agreement of the mujtahids of this ummah after the death of the Prophet (blessings and peace of Allah be upon him) on a shar‘i ruling.
By saying “agreement” we exclude differences of opinion; if there is a difference of opinion, even from one person, then we cannot say that there is ijmaa‘.
By saying “the mujtahids” we exclude the common folk and those who follow or imitate scholars; it does not matter whether they agree or disagree.
By saying “this ummah” we exclude the consensus of others, which carries no weight.
however there are problems with Ijma' as the rules as defined above are somewhat different between the madhabs or at least by the Imams of the madhabs as you showed off in your answer here.
An other problem is that some scholars have pretended Ijma' on issues which have no consensus such as ibn 'Abd al-Barr. Some explained this by saying he didn't know about differences or oppositions to the main opinion. On the other hand it is hard to tell about a consensus after the time of sahaba (r) or a consensus beyond the one of the 4 Imams.