What does "tenacity" mean?

Tenacity: That quality of bodies which keeps them from parting without considerable force; cohesiveness; the effect of attraction; -- as distinguished from brittleness, fragility, mobility, etc.

Additional senses

  1. 2.That quality of bodies which makes them adhere to other bodies; adhesiveness; viscosity. Holland.
  2. 3.(Physics) The greatest longitudinal stress a substance can bear without tearing asunder, -- usually expressed with reference to a unit area of the cross section of the substance, as the number of pounds per square inch, or kilograms per square centimeter, necessary to produce rupture.

Sources