In the event you would like to disassociate your Google account from your Flocabulary account you can easily do so in My Profile. Once logged in visit the My Profile page (in a drop-down menu under your name in the upper right corner).
When connected to a Google account you'll see in My Profile > My Account the following text: You are signed in via Google as firstname.lastname@example.org. (disconnect). Click on disconnect, and you'll be asked to set a Flocabulary.com password if you have not previously done so.
At this point you may begin using your Flocabulary.com user credentials (username and password), or if you'd like, you can connect your Flocabulary account to a different Google account.