1) to be about
1a) to be on the point of doing or suffering something
1b) to intend, have in mind, think to
Part of Speech: verb
A strengthened form of G3199 (through the idea of expectation); to intend, that is, be about to be, do, or suffer something (of persons or things, especially events; in the sense of purpose, duty, necessity, probability, possibility, or hesitation): - about, after that, be (almost), (that which is, things, + which was for) to come, intend, was to (be), mean, mind, be at the point, (be) ready, + return, shall (begin), (which, that) should (after, afterwards, hereafter) tarry, which was for, will, would, be yet.
|a be about to||67.62|
|b must be||71.36|
These two sites give similar information, with the definition from several dictionaries and statistics on the use of the word.
Perseus Digital Library
University of Chicago's Logion lexicon
Thayer's dictionary plus other information.
From this site's dictionary (in Italian)
Click on the first column to search for that word as a form of the root μέλλω; click on the second column to search for that grammatical form of the root μέλλω; click on the third column to search for that word and grammatical form; click on the total to search for the root μέλλω.