Look at the answers below and then start working with some words.
To begin with you can see that there are two meanings: Flour 1 is
a powder used for baking and Flour 2 means "to cover a surface
Flour 1 is a noun (=substantiv) -indicated by the n
Flour 1 can be pronounced in two ways; with or without the r at the end (look at the phonetics after the slash).
There are different kinds of flour: plain flour and self-raising flour.
a. Some English language dictionaries you can turn to are, for instance, Longman, Oxford, Cambridge or Merriam-Webster. Go to a bookshop and have a look which one you prefer.
b. A lot of dictionaries are available on the net. Go to "Your dictionary" (the URL is very easy to remember www.yourdictionary.com) and browse around. You'll find the most popular dictionaries as well as rhyming, synonyms etc. My favorite on the net is Cambridge.