A disk 
in a solid torus 
is called meridinal if its boundary is a nontrivial
curve in 
(so that it is a meridian). Then a closed subset 
is called geometrically essential in 
if 
intersects every piecewise linear meridinal disk in 
(Rolfsen 1976, p. 110).
Geometrically Essential
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References
Rolfsen, D. Knots and Links. Wilmington, DE: Publish or Perish Press, 1976.Referenced on Wolfram|Alpha
Geometrically EssentialCite this as:
Weisstein, Eric W. "Geometrically Essential." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/GeometricallyEssential.html