From the Latin jacere, to throw — the same source from which we get both eject and ejaculate — the noun jactancy means bragging or boasting.
This is one of those words that has more forms than it needs. Other attested noun forms are jactance, jactation, and jactitation, the last two of which can also refer to a shaking or tossing of the body, in a medical sense. One who boasts or spasms (or, I suppose, both) jactitates.
There also exists the legal term jactitation of marriage. It isn't
when a marriage goes into spasm; it is falsely boasting that one is
married to someone else to the point that one's common matrimonial
reputation may be compromised. If eHarmony cancels your account because a
wannabe lover convinces them that you're married, you may have grounds for a restraining order due to jactitation of marriage.
Friday is National Grammar Day, and the American Copy Editors Society is once again holding a Grammar Day haiku contest. I was a runner-up in this contest a few years ago. Since then, the prizes have gotten better, along with the quality of the entries. Feel free to enter.
I'll be entering again this year. I hope to do a little jactitation (of the braggadocio kind) when the winners are announced.
(A technical note: I use the Zemanta plug-in, which recommends available images based on the text I put in a blog post. It noticed I used the word ejaculate at the beginning. The images are not pretty.
This is life on the Internet.)