The Collaborative International Dictionary of English v.0.48:

Sorrow \Sor"row\, v. i. [imp. & p. p. Sorrowed; p. pr. & vb.
   n. Sorrowing.] [OE. sorowen, sorwen, sorhen, AS. sorgian;
   akin to Goth. sa['u]rgan. See Sorrow, n.]
   To feel pain of mind in consequence of evil experienced,
   feared, or done; to grieve; to be sad; to be sorry.
   [1913 Webster]

         Sorrowing most of all . . . that they should see his
         face no more.                            --Acts xx. 38.
   [1913 Webster]

         I desire no man to sorrow for me.        --Sir J.
                                                  Hayward.
   [1913 Webster]

WordNet (r) 3.0 (2006):

sorrowing
    adj 1: sorrowful through loss or deprivation; "bereft of hope"
           [syn: bereaved, bereft, grief-stricken, grieving,
           mourning(a), sorrowing(a)]