Source : Webster's Revised Unabridged Dictionary (1913)

Lissom \Lis"som\, Lissome \Lis"some\ (l[i^]s"s[u^]m), a. [For
   lithesome.]
   1. Limber; supple; flexible; lithe; lithesome.

            Straight, but as lissome as a hazel wand.
                                                  --Tennyson.

   2. Light; nimble; active. --Halliwell. -- {Lis"some*ness}, n.

Source : WordNet®

lissome
     adj : gracefully slender; moving and bending with ease [syn: {lissom},
            {lithe}, {lithesome}, {slender}, {supple}, {svelte}, {sylphlike}]