Definition of "bumptious"

[…] I was still annoyed at his bumptious style of conversation; I thought it best to change the topic.

1891, A[rthur] Conan Doyle, A Study in Scarlet. A Detective Story, 3rd edition, London, New York, N.Y.: Ward, Lock, Bowden, and Co., […], published 1892

From another point of view, it was a place without a soul. The well-to-do had hearts of stone; the rich were brutally bumptious; the Press, the Municipality, all the public men, were ridiculously, vaingloriously self-satisfied.

1918, W[illiam] B[abington] Maxwell, chapter XXII, in The Mirror and the Lamp, Indianapolis, Ind.: The Bobbs-Merrill Company

She could stand it no longer. It was full of prying old women, she said, who stared in one's face, and of bumptious young men who trod on one's toes.

1928, Virginia Woolf, Orlando: A Biography, London: The Hogarth Press; republished as Orlando: A Biography (eBook no. 0200331h.html), Australia: Project Gutenberg Australia, July 2015

No doubt of it, Edmund was at grips with that bumptious little hairy dog. They were going it at the very top note of sadistic fury, screaming and snip-snapping in such a lightning mixture of black and white murder that the eye could not follow it.

1938, Norman Lindsay, Age of Consent, 1st Australian edition, Sydney, N.S.W.: Ure Smith, published 1962, page 140