The Collaborative International Dictionary of English v.0.48:

Inulin \In"u*lin\, n. [From NL. Inula Helenium, the
   elecampane: cf. F. inuline.] (Chem.)
   A substance of very wide occurrence. It is found dissolved in
   the sap of the roots and rhizomes of many composite and other
   plants, as Inula, Helianthus, Campanula, etc., and is
   extracted by solution as a tasteless, white, semicrystalline
   substance, resembling starch, with which it is isomeric,
   having fructose units in place of most of the glucose units.
   It is intermediate in nature between starch and sugar, and
   replaces starch as the reserve food in Compositae. Called
   also dahlin, helenin, alantin, alant starch, etc.
   [1913 Webster +PJC]

The Collaborative International Dictionary of English v.0.48:

Dahlin \Dah"lin\ (d[aum]"l[i^]n), n. [From Dahlia.] (Chem.)
   A variety of starch extracted from the dahlia; -- called also
   inulin. See Inulin.
   [1913 Webster]

WordNet (r) 3.0 (2006):

inulin
    n 1: used to manufacture fructose and in assessing kidney
         function