I’d just like to quote a bit of an article from Biblical Greek Language and Lexicography a book definitely worth anyone’s time.
The reasons I want to quote it is that so very often we find ourselves appealing to the definitions in lexicons to make our argumentation regarding the meaning of a given word.
“But then one turns to Greek. We have not walked into a slum exactly, but the building are more closely spaced, the porch banisters often rickety, the lawns not so well kept. Approaching the dictionary, a Hellenist must remain cautious and light on the feet. Often enough none of the translations equivalents is exact for a given context; sometimes the definition is simply wrong; glosses are rather frequently wrong (at least by contemporary interpretation); information on syntax, typical expressions, orthographica, or dialectical forms is hit-or-miss; and the overview one gets of the word can be fundamentally flowed, since, lexicographical practice aside, the passages considered by the lexicographer were too few and too skewed in the types of material. And then there is the outmoded lexicographic technique itself. . . . there exists no independently conceived Greek dictionary. That is, the Diccionario is based on the LSJ, which is based on Passow, which is based on Schneider, which is based on Stephanus – we are now back to the sixteenth century – and Stephanus is itself based on the Byzantine lexica and encyclopedias, themselves complied from earlier sources. . . . It is axiomatic that certain meanings of words which do not appear until much later, or which appear only sporadically in what comes down to us, nonetheless enjoyed continuous usage. . . . This lack of a proper historical viewpoint is, in my view, the most profound deficiency in LSJ and its ancillaries” (77).
The context of this quote comes directly from a discussion expressing the amazement that one finds in the Latin Lexica.
Now, with that said, BDAG is very strong lexicon and in many respects is is better than the LSJ, BUT it still have the same fault of being a dictionary based on a dictionary based on a dictionary based on a dictionary, also going back to Stephanus and thus, also back to the Byzantine lexica and encyclopedias.
All this to say, read even BDAG critically. Check the texts it cites and then go back and check other texts, compare lexica with each other, how do they differ and how are they the same. And then, go check more texts that contain the word you’re studying. If you have the time, go back and study the word yourself in as many occurrences as possible.