A1

1. noun

a) A standard paper size, defined by ISO 216 to have dimensions: 841 x 594 mm (840.90 x 594.60 mm)

a sheet of A1 paper

b) Under the ("UIC") classification system, a steam locomotive that has two coupled driving wheels followed by two trailing wheels, with no leading wheels; also called an 0-2-2.

2. adjective

a) In good health.

b) In excellent or top condition.