An isolated point on a curve is more commonly known as an acnode.
An isolated point of a discrete set 
is a member of 
(Krantz 1999, p. 63).
In graph theory, Harary (1994, p. 15) uses the term isolated point for an isolated vertex.
Isolated Point
See also
Acnode, Discrete Set, Isolated Vertex, NeighborhoodExplore with Wolfram|Alpha
References
Harary, F. Graph Theory. Reading, MA: Addison-Wesley, 1994.Krantz, S. G. "Discrete Sets and Isolated Points." §4.6.2 in Handbook of Complex Variables. Boston, MA: Birkhäuser, pp. 63-64, 1999.Referenced on Wolfram|Alpha
Isolated PointCite this as:
Weisstein, Eric W. "Isolated Point." From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/IsolatedPoint.html