Incisive means "impressively direct and decisive." It is generally applied to either something communicated in a way that is very clear and direct, or to a person who is able to explain difficult ideas clearly and confidently.

// The columnist is known for her incisive commentary on local politics.

Diminution is a formal word that refers to the act or process of becoming less.

// The company is committed to seeing that efforts to scale up production do not result in a diminution of quality.

Nebulous is a formal word used to describe something that is difficult to see, understand, or describe—in other words, something indistinct or vague.

// A lot of philosophical concepts can seem nebulous at first, but a good instructor can cut through the jargon and help students see how they apply to day-to-day life.

Undulant describes things that rise and fall in waves, or things that have a wavy form, outline, or surface.

// The exhibit featured a painting with beautiful green strokes that resembled undulant hills.

Something may be described as flagrant if it is conspicuously bad—that is, too bad to be ignored.

// In a flagrant violation of the family's code of ethics, someone finished the ice cream and left the empty container in the freezer.

To validate something is to show that it is real or correct. Validate can also mean “to state or show that something is legal or official,” “to put a mark on something to show that it has been checked and is official or accepted,” and “to show that someone’s feelings, opinions, etc., are fair and reasonable.”

// The company’s claims about its latest product are yet to be validated.

// You can get discounted parking by having your parking garage ticket validated at the museum's ticket desk.

// The decline in sales only validated our concerns about the menu changes.

Something described as salient is very important or noticeable.

// The assignment was to write down the most salient points made in the article.

// One salient feature of the band's music is the variety of different genres it incorporates into a singular sound.

A euphemism is a mild or pleasant word or phrase that is used instead of one that is unpleasant or offensive.

// The HR department advises using the euphemism “let go” instead of saying that someone was fired.

Ostentatious describes someone or something that displays wealth, knowledge, power, etc., in a way that is meant to attract attention, admiration, or envy. Things that are ostentatious tend to stand out as overly elaborate or conspicuous.

// The resort town is famous for its extravagantly expensive summer homes, which some tourists view as impressive and others merely ostentatious.