If you’re looking in the lexicon at the entry for a word that is nom/voc, and you see an entry marked (c. gen.), does that mean you can exclude it from your list of meanings, since your word is nom/voc? Or do you include it in case it’s WITH a word that is genitive?
Sorry if that’s a dumb question. 
Thanks again
No questions are really dumb.
(c. gen.) means with the genitive so it indicates that the word (like the adjectives plenus, avidus, cupidus etc) may have have a dependent noun which will be in the genitive case. Do you have a specific example in mind?
Pretty sure this one is. 
So take ὄνειδος. It’s a noun, and it’s nom/voc/acc. That means the word, in context, can never be (c. gen.), and can never be translated “the reproach of”, even if the words before or after are genitive? Right?
Cheers
Whoops apologies wrong language. I must have been half asleep.
In the LSJ entry for ὄνειδος we find:
c. gen., τὸ . . πόλεως ὄ. the disgrace of the city, A. Th. 539;
So ὄνειδος takes the genitive case hence “πόλεως”.
Are you trying to tease out the difference between say “the fear of the city” ie fear that the inhabitants of the city feel and the “Fear of the city” which is the fear that others have of the city’s inhabitants? Its very late here I will try to post something tomorrow about this.
I think I have understood your question, but if I haven’t I am the stupid one…
The LSJ entry for ὄνειδος says first:
ὄνειδ-ος, εος, τό,
This means that the nominative form is ὄνειδος. Incidentally all neuter words have the same form in nom/voc/acc, but it is the nominative singular that is listed in dictionaries. The εος means that the genitive form is ὀνείδεος. The τό indicates that it is a neuter noun. So the noun can occur in any case or number, but the dictionary will only give you the nominative singular form and the genitive singular ending. This is generally what you need in order to know the rest of the declension, as long as you know your declension tables.
When it is in its genitive form ὀνείδεος, it will not mean “the reproach of”, but for instance “of the reproach” (but the genitive case can be used in very many other ways too). And as /u/seneca2008 has explained the c.gen means that the word can take a genitive object, so yes indeed, for example ὄνειδος τῆς πόλεως, would mean “disgrace of the city”, as LSJ has it.
It’s the genitive object thing. “Insult to the city” is stronger, imo.
οὐ μὴν ἀκόμπαστός γ’ ἐφίσταται πύλαις,
τὸ γὰρ πόλεως ὄνειδος ἐν χαλκηλάτωι
σάκει, κυκλωτῶι σώματος προβλήματι,
Σφίγγ’ ὠμόσιτον προσμεμηχανημένην
γόμφοις ἐνώμα, λαμπρὸν ἔκκρουστον δέμας,
φέρει δ’ ὑφ’ αὑτῆι φῶτα, Καδμείων ἕνα,
ὡς πλεῖστ’ ἐπ’ ἀνδρὶ τῶιδ’ ἰάπτεσθαι βέλη.
Enraging them, just enraging them with that Sphinx on his shield/armor.
You can see it even more in the next cite:
ἔτικτε γάρ μ’ ἔτικτεν, ὤμοι μοι κακῶν,
οὐκ εἰδότ’ οὐκ εἰδυῖα, καὶ τεκοῦσά με
αὑτῆς ὄνειδος παῖδας ἐξέφυσέ μοι.
Object object object…packing so much tension in there that it’s cranked up to 11.
For she bore me, bore for me (woe’s me these evils!)
me not knowing she not knowing, and having borne me
a shame to her, she discharged children for me.
[I don’t take second ἔτικτεν as absolute in the first line.]
Thanks.
Ok, so in the lexicon, sometimes it clearly says “with genitive”, so if the word is with a genitive it means so-and-so. But is that what the lexicon means when it says (c. gen.), or does it mean that the word (in our example ὄνειδος) means something when it is in the genitive case (say πόλεως).
But you aren’t looking up πόλεως. You’re looking up ὄνειδος, which isn’t genitive. So that means you can ignore the lexicon meanings that aren’t genitive, since your word isn’t genitive, Right?
Or does (c. gen.) really mean “with genitive” instead of “this word in genitive form”?
And what does “rei” mean? 
Cheers
Yes, “c.gen” means the word can take a genitive, not what its meaning is in genitive. That would have been just “gen.” I guess c. stands for Latin “cum”. Sometimes it will be “c. dat”, “c. acc. et inf.” or more complex like “c. dupl. acc. pers. et partis”. It takes some time to get used to this shorthand style, especially since LSJ is not consistent in the way it does this. Where did you find “rei”? It means “thing”, probably as opposed to “person”.
Thanks. I did say it was a dumb question.
Is there a glossary of this shorthand?
Cheers
The abbreviations always stumped me, coming to the LSJ without any Latin. I always hoped to find some guide, but never did. I’ll make a sticky thread here, and we can fill it out together.
EDIT: Before I make that thread, I notice that most (all?) of the abbreviations are in “V. General List of Abbreviations”, so maybe we just need Latin translations.
This url points to L&S Abridged, the abbreviations page:
https://archive.org/details/lexiconabridgedf00liddrich/page/n9/mode/2up
Here it is, cropped and color-enhanced:
Doesn’t have “rei” though. 
“Pass.” means passive voice, but “pass.” means passive signification. Learn something new every day.
There’s a longer list of abbreviations for the LSJ on the TLG:
http://stephanus.tlg.uci.edu/lexica.php
or Perseus: http://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.04.0057%3Afrontmatter%3D5
You can access the TLG lexica without a subscription, but I think you need to register (for free). On the TLG version of the LSJ there is a handy button that says “Show Abbrev.” for any entry.
That won’t help you with unabbreviated Latin like rei (for example in c. gen. rei=cum genitivo rei, “with the genitive of the thing”…in contrast to c. gen. pers(onae) with the genitive of the person). You might find this tutorial helpful:
Relatedly, see this handy list of mainly Latin abbreviations in critical apparatuses, some of which overlap with those used in dictionaries: http://udallasclassics.org/wp-content/uploads/maurer_files/APPARATUSABBREVIATIONS.pdf
For naughty words the whole definition is sometimes in Latin (eg βινέω, πυγίζω, εὐρύπρωκτος, ψωλή, ταῦρος III, several words defined as pudenda muliebria or membrum virile (female and male genitalia)). Or just avoided by “sens. obsc.” (=sensu obsceno, with obscene sense). The abridged versions for schoolboys often remove even these Latin workarounds. In those cases you’ll want a more recent dictionary, especially if you’re reading Aristophanes.
Thanks! What modern dictionary do you recommend?
Two decent options are The Cambridge Greek Lexicon and The Brill Dictionary of Ancient Greek. Thankfully, they are stripped of all the Victorian dressing of the LSJ, but they do not supersede the scholarship of the unabridged version (aka "The Great Scott”). The LSJ is the dictionary I use by far the most.
Ok, thanks!