bi-swing

[bahy-swing]
adjective
  1. (of a garment) made with a deep pleat starting at the back waistline or belt and extending up to the shoulder on each side, to avoid constriction when the wearer's arms are extended.
noun
  1. a garment made with such pleats at the back, especially a jacket.

Origin of bi-swing

First recorded in 1965–70
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018