The Collaborative International Dictionary of English v.0.48:

Sobbing \Sob"bing\, n.
   A series of short, convulsive inspirations, the glottis being
   suddenly closed so that little or no air enters into the
   lungs.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Sob \Sob\, v. i. [imp. & p. p. Sobbed (s[o^]bd); p. pr. & vb.
   n. Sobbing.] [OE. sobben; akin to AS. se['o]fian,
   si['o]fian, to complain, bewail, se['o]fung, si['o]fung,
   sobbing, lamentation; cf. OHG. s[=u]ft[=o]n, s[=u]ftj[=o]n,
   to sigh, MHG. siuften, siufzen, G. seufzen, MHG. s[=u]ft a
   sigh, properly, a drawing in of breath, from s[=u]fen to
   drink, OHG. s[=u]fan. Cf. Sup.]
   To sigh with a sudden heaving of the breast, or with a kind
   of convulsive motion; to sigh with tears, and with a
   convulsive drawing in of the breath.
   [1913 Webster]

         Sobbing is the same thing [as sighing], stronger.
                                                  --Bacon.
   [1913 Webster]

         She sighed, she sobbed, and, furious with despair.
         She rent her garments, and she tore her hair. --Dryden.
   [1913 Webster]

WordNet (r) 3.0 (2006):

sobbing
    n 1: convulsive gasp made while weeping [syn: sob, sobbing]

Moby Thesaurus II by Grady Ward, 1.0:

37 Moby Thesaurus words for "sobbing":
   bawling, blubbering, cry, crying, dissolved in tears,
   fit of crying, flood of tears, good cry, greet, in tears, lachryma,
   lachrymal, lachrymose, lachrymosity, lacrimatory, melting mood,
   moaning, overflowing eyes, ready to cry, sigh, sighing, sniveling,
   soughing, tear, tear bottle, teardrop, tearful, tearful eyes,
   tearfulness, tears, teary, weepiness, weeping, weepy, whimpering,
   whining, with eyes suffused