Sleeve that extends to neckline, set in by seams slanting from the underarm front and back. Used since mid-1850s. A variation is made with an additional seam down outside of arm called a three-seamed raglan.
FDF, 1988
Context:
Raglan sleeves, which are cut with seams that extend from shoulder to neck, always make a coat more casual.
The first part of the term, raglan, is an eponym, since it is derived from Fitzroy James Henry Somerset (1788–1855), First Baron of Raglan, British commander in the Crimean war.