I do realize this question might be difficult to answer as most words in Ancient Greek are hard to translate, and some have whole studies around them. But as there isn't a stack exchange for Ancient Greek, I figured this would be the best place to ask. I wonder if anyone have made an entire work around it, even if not a dictionary. Just some sort of guide to Greek vocabulary somehow.
There are quite a few - and they're not really hard to come by.
This answer cannot be an exhaustive survey of the Greek dictionary landscape, however it can get you started and past your first learning assignments.
First and foremost, consider the Liddell Scott Jones, which is GRE-ENG and a major authority. It's available in most Classics Libraries and has been digitalised by Tufts University, now going by the name of "Greek Word Study Tool".
There are also smaller Paperback dictionaries by OUP, and some by Collins.
Pupils and Undergrads in Germany often use the "Gemoll" GRE-GER dictionary, while there are a host of other offers, including specialist publications for theologians reading biblical texts in ancient Greek. Again, try the departmental library, they can help.
EDIT 27 Mar 2017:
- Digitised copy of A Greek-English Lexicon by H. G. Liddell and R. Scott to view on-screen and download at archive.org.
- Online searchable Greek Dictionary in the Perseus Digital Library.
- Gemoll: ISBN 978-3-637-00234-0, price tag now around 50 Euros, get one at your local library until you're really sure that Greek is for you (and there are good reasons that you might come to like it). Or have a look at antiquarian books instead.
Again, try searching your university OPAC or talking to faculty/library staff.