This word just… walks along and… bumps into you. And keeps walking. Noisy, obnoxious, maybe even raring for a fight, but definitely presumptuous. Perhaps rambunctious. But not necessarily a bumpkin. Merriam-Webster gives this example: “a bumptious young man whose family wealth gave him a sense of entitlement.” So certainly not scrumptious (let alone scrump-dilly-umptious). Maybe a bouncer, though more likely among the bounced, but not bouncy.
Bumptious keeps company with words such as arrogant and upstart. It’s a yob who wants everything to be sumptuous, and if it’s not – or even if it is – he will be abusive. It’s a crowd you do not want to be among, especially if you are a decent, sensible person. It’s the leader of that crowd, perhaps the aforementioned rich young man who has become a rich older man with no tempering of wisdom. Whoever it is, they’re fractious.
Fractious. Ah, now, that’s a nice erudite word, isn’t it. Originally ‘disposed to make fractures’, i.e., to break things literally or figuratively; now a white-coat word for ‘unruly’, usually followed by child. It is also – along with similar words such as captious – a model for bumptious. But unlike those other words, bumptious is not purely Latin. Someone took good old English bump and rudely jammed it onto the tious (not even the proper suffix, ous). Someone sometime around the year 1800.
The first sense of bumptious was not so noisy; it meant (as the Oxford English Dictionary puts it) ‘offensively self-conceited’. (Oxford adds that this word is colloquial and undignified.) It has since bumped up a bit more, to ‘obnoxiously self-assertive’ or words to that effect. Like those guys you can hear coming down the street before you see them, or that person who pushes in front of you in line, or any of the myriad louts who instantly earn the quiet acid condemnation of the genteel. But the dry anathemas of discomfited doyens are otiose: to the bumptious, they mean bupkes.