Mistaken or improper thought or opinion; an instance of this.

The condition of erring in opinion; the holding of mistaken notions or beliefs; an instance of this, a mistaken notion or belief; false beliefs…

The quality of being foolish or of holding erroneous opinions. Obsolete.

An error, fault; also, erroneous belief, heresy.

Irrational, deluded, or absurd thought, speech, or behaviour; delusion, absurdity. Also: an absurd, irrational, or deluded belief or remark.

Of doctrine, principles, etc.

Misunderstanding, spurious knowledge; a mistaken understanding.

The condition of erring or being in error.

The holding of false opinions, notions, or beliefs; (also) an instance of this; an erroneous belief.

Psychology. The erroneous perception of patterns or correlations in random or unconnected phenomena, events, and data.