intractable

From in- +‎ tractable

intractable (comparative more intractable, superlative most intractable)

1. Not tractable; not able to be managed, controlled, governed or directed.
   • 1972, Edsger W. Dijkstra, The Humble Programmer (EWD340):

     And I cannot but expect that this will repeatedly lead to the discovery that an initially intractable problem can be factored after all.

2. (mathematics) Not able to be solved (of a mathematical problem).
3. Stubborn; obstinate (of a person).
4. (medicine) Difficult to treat (of a medical condition).

• intractability
• intractableness
• intractably

• intractable in The Century Dictionary, New York, N.Y.: The Century Co., 1911.
• intractable in Webster’s Revised Unabridged Dictionary, G. & C. Merriam, 1913.