make-believe

Short definition from Wiktionary

Noun

1. 1
   The quality or act of pretending; acting as if something is true when in fact one knows it is not.
2. 2
   The condition of pretending or imagining that things are better than they really are.
3. 3
   Something imaginary.
4. 4
   Alternative form of make-believe.

Adjective

1. 1
   Imaginary; not real; pretend.
2. 2
   imaginary; conjured in someone's imagination, especially that of a child

Verb

1. 1
   To pretend or imagine.