Effulgence means “radiant splendor” or “brilliance.”

// Guests oohed and aahed at the sudden effulgence of the pagoda, as the last of its hundreds of candles were finally lit.

Tacit is a formal adjective used to describe something that is expressed or understood without being directly stated.

// As roommates, we had a tacit agreement that we would never pry into each other’s affairs.

Gambol means "to run or jump in a lively way." It is used as a synonym of frolic.

// There are few sights more charming than that of lambs gamboling about in a meadow in full flower.

Perfunctory is a formal word used to describe something that is done without energy or enthusiasm because of habit or because it is expected.

// By the time my favorite band got to the last stop of the tour, their performance felt perfunctory.

truth in speech or statement; truthfulness 

Someone or something described as sagacious has or shows an ability to understand difficult ideas and situations and to make good decisions. Sagacious may be considered a formal synonym of wise and discerning.

// Student reviews paint the writing professor as a sagacious mentor and a compassionate teacher.

A nabob is a very rich or important person.

// The upscale hotel downtown is a popular meeting spot for the city’s corporate nabobs.

Umami refers to the taste sensation that is produced by several amino acids and nucleotides and that has a rich or meaty flavor characteristic of cheese, cooked meat, mushrooms, soy, and ripe tomatoes.

// The chef’s secret ingredient added the perfect burst of umami to the signature dish.