unrealize

In sense 1, unreal +‎ -ize.

In sense 2, un- +‎ realize.

unrealize (third-person singular simple present unrealizes, present participle unrealizing, simple past and past participle unrealized)

1. (transitive) To make unreal; to idealize.
   • 1875, James Russell Lowell, Spenser‎:

     His fancy, habitually moving about in worlds not realized, unrealizes everything at a touch.

   • 1951, Journal of Literary History, page 39:

     But De Quincey generally sees a much deeper technical significance, an idealizing or unrealizing effect in the language.

   • 2002, Fernando Pessoa, The Book of Disquiet‎:

     Every action that realizes a dream or desire unrealizes it in reality.

2. (nonce word) To alter one's own viewpoint after a previous realization; to change one's mind.

   I easily realized that all of his statements were wrong. How do you unrealize that?

• neuralize