Sleeve cut as an extension of the bodice of a dress, blouse or jacket. The batwing sleeve is designed without a socket for shoulder, thus creating a deep, wide armhole that reaches from the waist to a narrowed wrist. It can also start higher up in the garment (for example half-way up the side seam), the important feature is that the armhole be wide. This type of sleeve was popular during the 30s.
FFD, 1998, Campbell, 2005
Context:
The batwing sleeve eliminates the curved seam that goes around the armhole, thus making the sleeve and bodice one piece. There may be a decorative seam that joins seam to body of garment, but it does not provide for shaping around the arm socket.