I think a lot of definitions of Islamophobia have been floating around. Dr. Jasmin Zine has a great definition of Islamophobia when she talks about widespread ideological and systemic expressions of Islamophobia. It's based on the fear of Muslims, but it's not restricted to a hyperbolic fear of Muslims.
I think her definition is sufficient, and I support it. I haven't come up with a definition of Islamophobia. I think in her use of that term and in her framing of it she thinks anti-Muslim is an expression of Islamophobia, but Islamophobia is broader than that.