solipsism
n. C2 Proficiency Oxford UK //sˈɒlɪpsˌɪzəm// solip·sism
n. the idea that only your own mind is real and you cannot be sure that anyone else exists. You can use it as a joke about someone who only thinks about themselves.
n. the philosophical theory that the self is the only entity that can be known to exist. Metaphorically used to describe extreme self-centredness.
Dealing with his solipsism makes having a real conversation almost impossible.
She joked that the driver's solipsism must be total if he thinks he owns the entire road.
The protagonist's spiral into absolute solipsism leads him to treat his oldest friends as mere figments of his imagination, ultimately severing his final connections to the objective world.
From Latin sōlus (“alone”) + ipse (“self”) + -ism.
Usage
often used as a noun, uncountable