beam-ends

beam-ends pl (plural only)

(nautical) The ends of the transverse beams of a ship.
- 1840, R[ichard] H[enry] D[ana], Jr., “CHAPTER XXXV”, in Two Years before the Mast. […] (Harper’s Family Library; no. CVI), New York, N.Y.: Harper & Brothers […], →OCLC:
  The ship is lying over half upon her beam-ends; lee scuppers under water, and forecastle all in a smother of foam.
- 1881–1882, Robert Louis Stevenson, Treasure Island, London; Paris: Cassell & Company, published 14 November 1883, →OCLC:
  It began to be chill; the tide was rapidly fleeting seaward, the schooner settling more and more on her beam-ends.

A ship is on her beam-ends when she has heeled over such that the beams are vertical and she cannot be brought back to an upright position.

English