The Collaborative International Dictionary of English v.0.48:

Sinew \Sin"ew\, n. [OE. sinewe, senewe, AS. sinu, seonu; akin to
   D. zenuw, OHG. senawa, G. sehne, Icel. sin, Sw. sena, Dan.
   sene; cf. Skr. sn[=a]va. [root]290.]
   [1913 Webster]
   1. (Anat.) A tendon or tendonous tissue. See Tendon.
      [1913 Webster]

   2. Muscle; nerve. [R.] --Sir J. Davies.
      [1913 Webster]

   3. Fig.: That which supplies strength or power.
      [1913 Webster]

            The portion and sinew of her fortune, her marriage
            dowry.                                --Shak.
      [1913 Webster]

            The bodies of men, munition, and money, may justly
            be called the sinews of war.          --Sir W.
                                                  Raleigh.
      [1913 Webster]

   Note: Money alone is often called the sinews of war.
         [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Sinew \Sin"ew\, v. t. [imp. & p. p. Sinewed; p. pr. & vb. n.
   Sinewing.]
   To knit together, or make strong with, or as with, sinews.
   --Shak.
   [1913 Webster]

         Wretches, now stuck up for long tortures . . . might,
         if properly treated, serve to sinew the state in time
         of danger.                               --Goldsmith.
   [1913 Webster]

WordNet (r) 3.0 (2006):

sinew
    n 1: a cord or band of inelastic tissue connecting a muscle with
         its bony attachment [syn: tendon, sinew]
    2: possessing muscular strength [syn: brawn, brawniness,
       muscle, muscularity, sinew, heftiness]