A supposition resting on no solid grounds; an arbitrary notion.

depreciative. A conception to which no reality corresponds; something merely imagined or fancied. Usually with modifying word, as mere.

Something imagined; a fanciful notion; a fancy. Obsolete. rare.

A product of fictitious invention. Something which exists only as an arbitrarily framed notion of the mind. a figment of (theor one's) imagination.

Hence spec. A groundless or insufficiently grounded supposition; a mere assumption or guess.

Chiefly depreciative. A supposition or idea.

A non-thing, vague abstraction, or concept having no properties.