(rail transport, UK) A principle in railway signalling where only one train or locomotive is allowed to run on a section of single-track line, such as a branch line, at any one time.

(education) Occurring while a class or lesson is taking place.

A village and civil parish in Derbyshire Dales district, Derbyshire, England (OS grid ref SK1969).

(education) A mathematical question on a test in which the answer must be placed on a grid that is preprinted on the answer sheet.

Alternative spelling of glycemic index.

A variant of castles in the air.

(obsolete) In prosperous circumstances; comfortably-off.

In a single attempt. / (theater) Performed downstage between the frontmost pieces of scenery.

(finance, historical) The first (1970s) attempt at European monetary cooperation, essentially pegging all of the EEC currencies to one another.

(British spelling) Alternative form of honor in the breach.