An older term, hardly used nowadays (2000), for an isolated point, or hermit point, of a plane algebraic curve.
For instance, the point $(0,0)$ is an acnode of the curve $X^3+X^2+Y^2=0$ in $\RR^2$.
- [a1] R.J. Walker, "Algebraic curves", Princeton Univ. Press (1950) (Reprint: Dover 1962)
Acnode. Encyclopedia of Mathematics. URL: http://encyclopediaofmath.org/index.php?title=Acnode&oldid=52716