What is "to shake out a reef"

Shake \Shake\, v. t. [imp. Shook; p. p. Shaken, ( Shook, obs.); p. pr. & vb. n. Shaking.] [OE. shaken, schaken, AS. scacan, sceacan; akin to Icel. & Sw. skaka, OS. skakan, to depart, to flee. [root]16

1. Cf. Shock, v.] 1. To cause to move with quick or violent vibrations; to move rapidly one way and the other; to make to tremble or shiver; to agitate.

   As a fig tree casteth her untimely figs, when she is shaken of a mighty wind.
   --Rev. vi. 13.

   Ascend my chariot; guide the rapid wheels That shake heaven's basis.
   --Milton.

2. Fig.: To move from firmness; to weaken the stability of; to cause to waver; to impair the resolution of.

   When his doctrines grew too strong to be shook by his enemies, they persecuted his reputation.
   --Atterbury.

   Thy equal fear that my firm faith and love Can by his fraud be shaken or seduced.
   --Milton.

3. (Mus.) To give a tremulous tone to; to trill; as, to shake a note in music.

4. To move or remove by agitating; to throw off by a jolting or vibrating motion; to rid one's self of; -- generally with an adverb, as off, out, etc.; as, to shake fruit down from a tree.

   Shake off the golden slumber of repose.
   --Shak.

   'Tis our fast intent To shake all cares and business from our age.
   --Shak.

   I could scarcely shake him out of my company.
   --Bunyan.

   To shake a cask (Naut.), to knock a cask to pieces and pack the staves.

   To shake hands, to perform the customary act of civility by clasping and moving hands, as an expression of greeting, farewell, good will, agreement, etc.

   To shake out a reef (Naut.), to untile the reef points and spread more canvas.

   To shake the bells. See under Bell.

   To shake the sails (Naut.), to luff up in the wind, causing the sails to shiver.
   --Ham. Nav. Encyc.