Strong's Concordance has some basic definitions, but I sometimes wanted more detail.
After doing a little research, I found that "Vines" was referenced quite a bit.
So I found a copy and have found it very useful myself not only for giving a definition, but also for providing some context around a word.
Bibliography Info:
Vines Complete Expository Dictionary of Old and New Testament Words
By W.E. Vine, Merrill F. Unger, William White, Jr.
Copyright 1985 Thomas Nelson Inc., Publishers
ISBN 90-8407-7559-8