I was reading a description of the Boeing X-45 that described it as having "lambda wings." What is a lambda wing and why is it called that?
Indeed, it is due to resemblance with Greek letter 'lambda', though not the capital one ($ \Lambda $), but the small one: $ \lambda $.
I am attaching a pic of X-45 with me drawing a lambda over it. Typically, the wing has two taper ratios. The inboard wing tapers heavily, corresponding to legs of small lambda, and the outboard wing tapers slightly or do not taper at all.
It's because the shape of the wing resembles the uppercase Greek letter lambda with the leading and trailing edges having the same sweep angle.