The definition of a figment is something imagined.
When you believe that a monster lives under your bed and there is no monster living there, the monster is an example of a figment of your imagination.
something merely imagined or made up in the mind
Origin of figmentMiddle English ; from Classical Latin figmentum ; from fingere, to form: see dough
Something invented, made up, or fabricated: just a figment of the imagination.
Origin of figmentMiddle English, from Latin figmentum, from fingere, to form; see dheigh- in Indo-European roots.
- Often used in the form "a figment of [someone's] imagination".