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1.
Sillster is a noun used to describe someone who acts in a goofy manner, usually with the word silly placed as an adjective before it.

It can also be used in a derogatory way to mock someone for being ignorant.
Girl: Would you like to be my boyfriend, and take me out on dates, and tell me how much you love me?

Boy(laughing): Stop being a silly sillster, and take your shirt off!
by Nilbog_gobliN May 14, 2012