“Farewell the neighing steed and the shrill trump, The spirit-stirring drum, th’ear-piercing fife, The royal banner, and all quality, Pride, pomp, and circumstance of glorious war!”
The phrase may seem familiar to you from the musical piece “Pomp and Circumstance Military Marches, Op. 39” by Sir Edward Elgar, often heard at graduation ceremonies.Given these two contexts, one may be able to deduce that the meaning hasn’t changed too drastically since Shakespeare’s time. Pomp is derived from the Greek word “pompa” meaning procession, and is used to describe something of “magnificence and splendor”. (Pomp, used in its negative form, describes “an ostentatious display of wealth or ceremony” lending the adjective “pompous”, which originally meant simply “characterized by pomp” but now means “self-important or arrogant.”) Circumstance, in this phrase, is used in its singular form, and means “the ‘ado’ made about anything; formality, ceremony, about any important event or action”. We commonly use the plural form “circumstances” in a similar way to describe “a fact or condition connected with or relevant to an event or action”.
The phrase “pomp and circumstance” thus means a magnificent display with surrounding fuss and/or importance. I think graduation ceremonies capture the essence of this phrase quite well. The “pomp” is the ceremony itself of graduates being celebrated, and the circumstance is demonstrated by those attending the event to witness and celebrate the achievements of the graduates, many of whom take photos and videos to commemorate the event.