Cusp
WordNet
noun
(1) Point formed by two intersecting arcs (as from the intrados of a Gothic arch)
(2) Small elevation on the grinding surface of a tooth
(3) A thin triangular flap of a heart valve
WiktionaryText
Etymology
From , the use in astrology was the first one to be used.
Noun
- A sharp point or pointed end.
- An important moment when a decision is made that will determine future events.
- A point of a curve where the curve is continuous but has no derivative, but such that it has a derivative at every nearby point.
- A boundary between zodiacal signs and houses.
- Any of the pointed parts of a canine tooth or molar.