Definition of portentiously in US English:

portentiously

adverb

  • 1In a manner which portends or foreshadows something; ominously.

  • 2Grandiloquently; in a self-important or pretentious manner.

Origin

Early 19th century; earliest use found in James Grahame (1765–1811), poet. From portentious + -ly.

Pronunciation

portentiously

/pɔːˈtɛnʃəsli/