great: outsized in bulk, in worth, or in the swagger of what is said
This word belongs to the book of Daniel alone, and it never describes just one thing. It comes out whenever several things at once are bigger than they ought to be: four beasts heaving up out of the sea, the iron teeth in the jaws of the fourth one, the heap of presents a king pushes on the man who has just read his dream, the signs God works where the whole world can see them.
From bulk to boasting is a short step. When the little horn opens a mouth speaking "great things", nothing is actually large. The words are simply outsized, swollen past the speaker who says them, and Daniel keeps returning to the phrase in Daniel 7:8, 7:11 and 7:20 until it is clear that the mouth is the real charge against the last king. Aramaic needed no separate word for arrogance here. It just called the words big.
Two neighbors stay clear of it. The singular (רַב) describes one thing at a time and can also work as a job title, the "chief" set over some body of royal servants, which this word never does. The word for quantity (שַׂגִּיא) counts instead of sizing up, and Daniel 2:48 lines the two up in a single breath: gifts that were both big and many.