Meaning

noun speaking of yourself in superlatives

noun (law) a false boast that can harm others; especially a false claim to be married to someone (formerly actionable at law)

noun (pathology) extremely restless tossing and twitching usually by a person with a severe illness

originFrom Medieval Latin jactitio, from iactitō (“throw, fling; boast, brag; utter, mention”).

Etymology from Wiktionary, CC BY-SA 3.0