From WordNet (r) 2.0 (August 2003) [wn]:
flavourless
adj : lacking taste or flavor or tang; "a bland diet"; "insipid
hospital food"; "flavorless supermarket tomatoes";
"vapid beer"; "vapid tea" [syn: bland, flat,
flavorless, insipid, savorless, savourless,
vapid]
From The Collaborative International Dictionary of English v.0.48 [gcide]:
flavourless \flavourless\ adj.
same as flavorless. [Chiefly Brit.]
Syn: bland, flat, flavorless, insipid, savorless.
[WordNet 1.5]