(masonry) A bond in which no header stone stretches across the wall, but two headers meet in the middle, and their joint is covered by another stone laid header fashion.

Lightning that occurs too far away for the resulting thunder to be audible by the observer.

With enthusiastic cooperation.

(engineering) A form of cam shaped like a heart, used to convert uniform rotary motion into uniform reciprocating motion.

A heavy optical glass, consisting essentially of potassium borosilicate.

(informal) Completely; wholly; hopelessly; head over heels.

(historical, Ireland) A rudimentary school in 18th- and 19th-century Ireland, held outdoors or in a house or barn.

A ring for fastening a scythe blade to the snath.

(historical) Either of a pair of large copper hemispheres, with mating rims, that were used to demonstrate the power of atmospheric pressure. When the rims were sealed with grease and the air was pumped out, the sphere contained a vacuum and could not be pulled apart even by teams of horses.

(obsolete, idiomatic) Negligently; rashly; without seeing what one does.