The Collaborative International Dictionary of English v.0.48:

Spindly \Spin"dly\, a.
   Long and slender, or disproportionately tall and slender; as,
   spindly legs.. Used in some cases to suggest weakness.

   Syn: spindling. [PJC]

WordNet (r) 3.0 (2006):

spindly
    adj 1: long and lean [syn: lank, spindly]

Moby Thesaurus II by Grady Ward, 1.0:

43 Moby Thesaurus words for "spindly":
   bony, dilapidated, doddering, flat, flat-chested, fleshless,
   gangling, gangly, gaunt, gawky, groggy, lank, lanky, lean,
   lean-fleshed, lean-looking, meager, ramshackle, rangy, rawboned,
   ricketish, rickety, rocky, scraggy, scrawny, shaky, skeletal,
   skinny, spare, spidery, spindling, teetering, teetery,
   thin-bellied, thin-fleshed, tottering, tottery, tumbledown, twiggy,
   undersized, underweight, unsteady, wobbly