1. 
[syn: bland, flat, flavorless, flavourless, insipid, savorless, savourless, vapid]
The Collaborative International Dictionary of English v.0.48:
flavourless \flavourless\ adj.
   same as flavorless. [Chiefly Brit.]
   Syn: bland, flat, flavorless, insipid, savorless.
        [WordNet 1.5]
WordNet (r) 3.0 (2006):
flavourless
    adj 1: lacking taste or flavor or tang; "a bland diet"; "insipid
           hospital food"; "flavorless supermarket tomatoes"; "vapid
           beer"; "vapid tea" [syn: bland, flat, flavorless,
           flavourless, insipid, savorless, savourless,
           vapid]