cusp

As a noun cusp

is a sharp point or pointed end.

As an adjective undefined is

lacking a definition or value.

As nouns the difference between cusp and boundary

is that cusp is a sharp point or pointed end while boundary is the dividing line or location between two areas.

As nouns the difference between precipice and cusp

is that precipice is a very steep cliff while cusp is a sharp point or pointed end.

As a noun cusp

is a sharp point or pointed end.

As an acronym crest is

(military) the five types of verbal support used to enhance an (oral) presentation: comparisons, reasons, examples, statistics, testimony.

As a proper noun ridge

is after a natural landscape feature.

As a noun cusp is

a sharp point or pointed end.

As nouns the difference between mucro and cusp

is that mucro is (botany|zoology) a pointed end, often sharp, abruptly terminating an organ, such as a projection at the tip of a leaf; the posterior tip of a cuttlebone; or the distal part of the furcula in collembola while cusp is a sharp point or pointed end.

As nouns the difference between flap and cusp

is that flap is anything broad and flexible that hangs loose, or that is attached by one side or end and is easily moved while cusp is a sharp point or pointed end.

As a verb flap

is to move (something broad and loose) back and forth.

As nouns the difference between cusp and threshold

is that cusp is a sharp point or pointed end while threshold is the bottom-most part of a doorway that one crosses to enter; a sill.

As a noun cusp

is a sharp point or pointed end.

As an adjective arcuate is

curved into the shape of a bow.

As nouns the difference between moot and cusp

is that moot is size, measure while cusp is a sharp point or pointed end.