Used to describe one's state of allergic plight, typically during hay-fever season. A sneezable person may sneeze at random or awkward moments, sneeze several times in a row, and/or will most likely not have tissues on hand.
"AahCHOO! Aah...CHOO aah CHOO! Ugh...sorry, I'm so sneezable today..."
"Whatever, dude...just - stop wiping your boogery hand on my sleeve..."