This playful exchange

word

is actually important and relevant to agnosticism.
You define Santa in very
specific terms (he distributes gifts, he climbs down chimneys, etc.). And since those terms fail to pass inspection, you conclude (quite sensibly) that Santa doesnt exist. It turns out that if a definition is
specific enough, one can actually prove a negative show that absence of evidence
is evidence of absence. On the other hand, if the definition is vague or infinitely elastic, no negative proof is possible. I.e., if we posit that Santa is a metaphysical spirit, conceptually sophisticated and doesnt manifest himself in any obvious or unambiguous ways, then theres no argument that
completely rules out his existence. So, strictly speaking, we should be agnostic.
Now
if it seems odd to be so scrupulously open-minded about Santa when - for all practical purposes - his non-existence has been well established, then I entirely agree. And its that very same rationale that informs the atheist perspective with respect to gods. True, gods can be defined in such a way as to be elusive with respect to direct evidence and, therefore, immune to disproof. But thats fairly weak sauce. For most other concepts (Santa, celestial teapots, pink unicorns and invisible dragons) we feel no need to resort to agnosticism because of a philosophical technicality; we simply and unapologetically say, I dont believe in Santa Im an a-Santa-ist.
And as a matter of intellectual consistency, the same standards must/should apply to the question of gods. I.e., atheism, not agnosticism.