What is the definition of word grumptious?

"Grumptious" is not a recognized word in the English language. It's likely a playful or invented word, perhaps a combination of "grumpy" and "stupendous" or "umptious" (which itself is not a real word).

If someone uses "grumptious," it's probably meant to describe something that is both grumpy and impressive or large in some way.

For example, they might say: "That was a grumptious storm!" meaning the storm was both powerful and unpleasant.

However, without context, it's hard to know the exact intended meaning of "grumptious."