1) Comprehend 2) Have illusions 3) Perceive 4) Perceive what is not there 5) Sense the unreal 6) To experience a hallucination 7) To have visions 1) Imagine 
• (v. i.) To wander; to go astray; to err; to blunder; -- used of mental processes.
Hal·lu'ci·nate (hăl*lū'sĭ*nāt) intransitive verb [ Latin hallucinatus , alucinatus , past participle of hallucinari , alucinari , to wander in mind, talk idly, dream.] To wander; to go astray; to err; to blunder; -- used of mental processes. [ R.] ...
[v] - perceive what is not there
verb perceive what is not there; have illusions