Definition of "intractable"

intractable

/ɪnˈtɹæk.tə.bəl/

adjective
comparative more intractable, superlative most intractable
1. Not tractable; not able to be managed, controlled, governed or directed.
  Quotations
  And I cannot but expect that this will repeatedly lead to the discovery that an initially intractable problem can be factored after all.
  1972, Edsger W. Dijkstra, The Humble Programmer (EWD340)
2. (mathematics) (of a mathematical problem) Not able to be solved in polynomial time; too difficult to attempt to solve.
3. Difficult to deal with, solve, or manage. (of a problem)
4. Stubborn; obstinate. (of a person)
5. (medicine) Difficult to treat (of a medical condition).