(idiomatic) Something of particular interest or concern; an obsession.

The experience of complex visual hallucinations in patients with visual loss.

(simile, humorous) Synonym of on it (“actively working to solve a problem, etc.”)

(historical) A kind of woman's bonnet, shaped like an inverted coal scuttle.

(mathematics) An important statement about surfaces in differential geometry, connecting their geometry (in the sense of curvature) to their topology (in the sense of the Euler characteristic).

Synonym of bee in one's bonnet

plural of bee in one's bonnet

A rare medical condition characterized by a vascular malformation extending from the craniofacial to the orbital regions and the brain.

plural of bonnetstring

(usually in the plural) A string that fastens a bonnet on the wearer's head.