The Collaborative International Dictionary of English v.0.48:

Leggy \Leg"gy\ (l[e^]g"g[y^]), a.
   1. having tall spindly stems; -- of plants. [WordNet sense 1]

   Syn: tall-growing.
        [WordNet 1.5]

   2. Having long legs. [WordNet sense 2] --Thackeray.

   Syn: long-legged, long-shanked.
        [1913 Webster]

WordNet (r) 3.0 (2006):

leggy
    adj 1: (of plants) having tall spindly stems [syn: leggy,
           tall-growing]
    2: having long legs [syn: leggy, long-legged, long-
       shanked]