Noun

1. The action of the verb to split.
2. A division in the mind, or affecting one's sense of self.
   • 2007, Brett Kahr, Sex and the Psyche, Penguin 2008, p. 308:

     In other words, something troubling, such as being discovered in the toilets in a shaming way, can be both remembered and also pushed to the periphery of consciousness, a process that psychotherapists refer to as ‘splitting’.

3. The cleavage of a covalent bond.

Adjective

1. resembling the sound of something being split or ripped
2. severe

   I have a splitting headache.