- noting a vessel regarded by a shipping-classification society as being equipped to the highest standard and with equipment maintained in first-class condition.
- Also A number one. Informal. first-class; excellent; superior: The meals there are A one.
Also A-one, A 1, A-1.
Origin of A one
First recorded in 1830–40
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018