1. [v]  decrease in size, range, or extent; "His earnings shrank"; "My courage shrivelled when I saw the task before me"
2. [v]  wither, esp. with a loss of moisture; "The fruit dried and shriveled"

SHRIVEL is a 7 letter word that starts with S.

1. \Shriv"el\, v. i. [imp. & p. p. {Shriveled}or
   {Shrivelled}; p. pr. & vb. n. {Shriveling} or {Shrivelling}.]
   [Probably akin to shrimp, shrink; cf. dial. AS. screpa to
   pine away, Norw. skrypa to waste, skryp, skryv, transitory,
   frail, Sw. skr["o]pling feeble, Dan. skr["o]belig, Icel.
   skrj?pr brittle, frail.]
   To draw, or be drawn, into wrinkles; to shrink, and form
   corrugations; as, a leaf shriveles in the hot sun; the skin
   shrivels with age; -- often with up.
   
   

2. \Shriv"el\, v. t.
   To cause to shrivel or contract; to cause to shrink onto
   corruptions.