The Collaborative International Dictionary of English v.0.48:

Tinny \Tin"ny\, a.
   Pertaining to, abounding with, or resembling, tin. "The tinny
   strand." --Drayton.
   [1913 Webster]

WordNet (r) 3.0 (2006):

tinny
    adj 1: of or containing tin
    2: of very poor quality; flimsy [syn: bum, cheap, cheesy,
       chintzy, crummy, punk, sleazy, tinny]
    3: thin and metallic in sound; lacking resonance; "an unpleasant
       tinny voice"

Moby Thesaurus II by Grady Ward, 1.0:

87 Moby Thesaurus words for "tinny":
   Mickey Mouse, aureate, base, brass, brassy, brazen, bronze, bronzy,
   cheap, cheesy, choked, coarse, common, copper, coppery, cracked,
   croaking, croaky, cupreous, cuprous, dry, ferrous, ferruginous,
   flimsy, fourth-class, gilt, gold, gold-filled, gold-plated, golden,
   gruff, guttural, harsh, harsh-sounding, hoarse, husky, inferior,
   iron, ironlike, irregular, lead, leaden, low-class, low-grade,
   low-quality, low-test, mean, mercurial, mercurous, metallic,
   nickel, nickelic, nickeline, paltry, pewter, pewtery, poor, punk,
   quicksilver, ragged, raucid, raucous, rough, roupy, rude,
   second-best, second-class, seedy, shabby, shoddy, silver,
   silver-plated, silvery, squawking, squawky, steel, steely,
   stertorous, strangled, tacky, tawdry, thick, third-class,
   third-rate, throaty, tin, twangy