There are many online Mandarin (Chinese) dictionaries. I found 词库 (Ci Ku) is one of the best. It is very easy to use. You can search by Pin Yin or hand writing and even by English word. It not only gives the definition of the word but also a lot of sentence examples. The best function is the stroke demonstration, so you can follow the stroke order to write Mandarin (Chinese) characters. Try it and let us what do you think.