Do I have public permission to quote definitions in a book from Merriam-Webster Dictionary?

I am a self publishing author who is in the process of publishing my work. I am sending it to the printing press tomorrow. And as far as copyrighting goes, everything is all squared away, accept that I used a couple of definitions from the m-w.com (Merriam Webster dictionary online), and as far as copyright goes, it is not exactly clear the terms and conditions that I may use definitions from it. Do I need to have permission to use several definitions?